EMBOSS: water

| water

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## Function

Smith-Waterman local alignment of sequences

## Description

water uses the Smith-Waterman algorithm (modified for speed enhancments) to calculate the local alignment of a sequence to one or more other sequences. The gap insertion penalty, gap extension penalty and substitution matrix used to calculate the alignments are specified. The output is a standard EMBOSS alignment file.

### Algorithm

The Smith-Waterman algorithm is a member of the class of algorithms that can calculate the best score and local alignment in the order of mn steps, where `n` and `m` are the lengths of the two sequences. These dynamic programming algorithms were first developed for protein sequence comparison by Smith and Waterman, though similar methods were independently devised during the late 1960's and early 1970's for use in the fields of speech processing and computer science.

Dynamic programming methods ensure the optimal local alignment by exploring all possible alignments and choosing the best. It does this by reading in a scoring matrix that contains values for every possible residue or nucleotide match. water finds an alignment with the maximum possible score where the score of an alignment is equal to the sum of the matches taken from the scoring matrix.

An important problem is the treatment of gaps, i.e., spaces inserted to optimise the alignment score. A penalty is subtracted from the score for each gap opened (the 'gap open' penalty) and a penalty is subtracted from the score for the total number of gap spaces multiplied by a cost (the 'gap extension' penalty). Typically, the cost of extending a gap is set to be 5-10 times lower than the cost for opening a gap.

There are two ways to compute a penalty for a gap of n positions : gap opening penalty + (n - 1) * gap extension penalty gap penalty + n * gap length penalty

The two methods are basically equivalent. The first way is used by EMBOSS and WU-BLAST. The second way is used by NCBI-BLAST, GCG, Staden and CLUSTAL. Fasta used it for a long time the first way, but Prof. Pearson decided recently to shift to the second.

The Smith-Waterman algorithm contains no negative scores in the path matrix it creates. The algorithm starts the alignment at the highest path matrix score and works backwards until a cell contains zero. See the Reference Smith et al. for details.

## Usage

Here is a sample session with water

    % water tsw:hba_human tsw:hbb_human
    Smith-Waterman local alignment of sequences
    Gap opening penalty [10.0]:
    Gap extension penalty [0.5]:
    Output alignment [hba_human.water]:

Go to the input files for this example
Go to the output files for this example

## Command line arguments

    Smith-Waterman local alignment of sequences
    Version: EMBOSS:6.5.6.0

       Standard (Mandatory) qualifiers:
      [-asequence]         sequence   Sequence filename and optional format, or
                                      reference (input USA)
      [-bsequence]         seqall     Sequence(s) filename and optional format, or
                                      reference (input USA)
       -gapopen            float      [10.0 for any sequence] The gap open penalty
                                      is the score taken away when a gap is
                                      created. The best value depends on the
                                      choice of comparison matrix. The default
                                      value assumes you are using the EBLOSUM62
                                      matrix for protein sequences, and the
                                      EDNAFULL matrix for nucleotide sequences.
                                      (Number from 0.000 to 100.000)
       -gapextend          float      [0.5 for any sequence] The gap extension
                                      penalty is added to the standard gap penalty
                                      for each base or residue in the gap. This
                                      is how long gaps are penalized. Usually you
                                      will expect a few long gaps rather than many
                                      short gaps, so the gap extension penalty
                                      should be lower than the gap penalty. An
                                      exception is where one or both sequences are
                                      single reads with possible sequencing
                                      errors in which case you would expect many
                                      single base gaps. You can get this result by
                                      setting the gap open penalty to zero (or
                                      very low) and using the gap extension
                                      penalty to control gap scoring. (Number from
                                      0.000 to 10.000)
      [-outfile]           align      [*.water] Output alignment file name
                                      (default -aformat srspair)

       Additional (Optional) qualifiers:
       -datafile           matrixf    [EBLOSUM62 for protein, EDNAFULL for DNA]
                                      This is the scoring matrix file used when
                                      comparing sequences. By default it is the
                                      file 'EBLOSUM62' (for proteins) or the file
                                      'EDNAFULL' (for nucleic sequences). These
                                      files are found in the 'data' directory of
                                      the EMBOSS installation.

       Advanced (Unprompted) qualifiers:
       -[no]brief          boolean    [Y] Brief identity and similarity

       Associated qualifiers:

       "-asequence" associated qualifiers
       -sbegin1            integer    Start of the sequence to be used
       -send1              integer    End of the sequence to be used
       -sreverse1          boolean    Reverse (if DNA)
       -sask1              boolean    Ask for begin/end/reverse
       -snucleotide1       boolean    Sequence is nucleotide
       -sprotein1          boolean    Sequence is protein
       -slower1            boolean    Make lower case
       -supper1            boolean    Make upper case
       -scircular1         boolean    Sequence is circular
       -sformat1           string     Input sequence format
       -iquery1            string     Input query fields or ID list
       -ioffset1           integer    Input start position offset
       -sdbname1           string     Database name
       -sid1               string     Entryname
       -ufo1               string     UFO features
       -fformat1           string     Features format
       -fopenfile1         string     Features file name

       "-bsequence" associated qualifiers
       -sbegin2            integer    Start of each sequence to be used
       -send2              integer    End of each sequence to be used
       -sreverse2          boolean    Reverse (if DNA)
       -sask2              boolean    Ask for begin/end/reverse
       -snucleotide2       boolean    Sequence is nucleotide
       -sprotein2          boolean    Sequence is protein
       -slower2            boolean    Make lower case
       -supper2            boolean    Make upper case
       -scircular2         boolean    Sequence is circular
       -sformat2           string     Input sequence format
       -iquery2            string     Input query fields or ID list
       -ioffset2           integer    Input start position offset
       -sdbname2           string     Database name
       -sid2               string     Entryname
       -ufo2               string     UFO features
       -fformat2           string     Features format
       -fopenfile2         string     Features file name

       "-outfile" associated qualifiers
       -aformat3           string     Alignment format
       -aextension3        string     File name extension
       -adirectory3        string     Output directory
       -aname3             string     Base file name
       -awidth3            integer    Alignment width
       -aaccshow3          boolean    Show accession number in the header
       -adesshow3          boolean    Show description in the header
       -ausashow3          boolean    Show the full USA in the alignment
       -aglobal3           boolean    Show the full sequence in alignment

       General qualifiers:
       -auto               boolean    Turn off prompts
       -stdout             boolean    Write first file to standard output
       -filter             boolean    Read first file from standard input, write
                                      first file to standard output
       -options            boolean    Prompt for standard and additional values
       -debug              boolean    Write debug output to program.dbg
       -verbose            boolean    Report some/full command line options
       -help               boolean    Report command line options and exit. More
                                      information on associated and general
                                      qualifiers can be found with -help -verbose
       -warning            boolean    Report warnings
       -error              boolean    Report errors
       -fatal              boolean    Report fatal errors
       -die                boolean    Report dying program messages
       -version            boolean    Report version number and exit

Qualifier | Type | Description | Allowed values | Default
--- | --- | --- | --- | ---
Standard (Mandatory) qualifiers
[-asequence] (Parameter 1) | sequence | Sequence filename and optional format, or reference (input USA) | Readable sequence | Required
[-bsequence] (Parameter 2) | seqall | Sequence(s) filename and optional format, or reference (input USA) | Readable sequence(s) | Required
-gapopen | float | The gap open penalty is the score taken away when a gap is created. The best value depends on the choice of comparison matrix. The default value assumes you are using the EBLOSUM62 matrix for protein sequences, and the EDNAFULL matrix for nucleotide sequences. | Number from 0.000 to 100.000 | 10.0 for any sequence
-gapextend | float | The gap extension penalty is added to the standard gap penalty for each base or residue in the gap. This is how long gaps are penalized. Usually you will expect a few long gaps rather than many short gaps, so the gap extension penalty should be lower than the gap penalty. An exception is where one or both sequences are single reads with possible sequencing errors in which case you would expect many single base gaps. You can get this result by setting the gap open penalty to zero (or very low) and using the gap extension penalty to control gap scoring. | Number from 0.000 to 10.000 | 0.5 for any sequence
[-outfile] (Parameter 3) | align | Output alignment file name | (default -aformat srspair) | <*>.water
Additional (Optional) qualifiers
-datafile | matrixf | This is the scoring matrix file used when comparing sequences. By default it is the file 'EBLOSUM62' (for proteins) or the file 'EDNAFULL' (for nucleic sequences). These files are found in the 'data' directory of the EMBOSS installation. | Comparison matrix file in EMBOSS data path | EBLOSUM62 for protein EDNAFULL for DNA
Advanced (Unprompted) qualifiers
-[no]brief | boolean | Brief identity and similarity | Boolean value Yes/No | Yes
Associated qualifiers
"-asequence" associated sequence qualifiers
-sbegin1 -sbegin_asequence | integer | Start of the sequence to be used | Any integer value | 0
-send1 -send_asequence | integer | End of the sequence to be used | Any integer value | 0
-sreverse1 -sreverse_asequence | boolean | Reverse (if DNA) | Boolean value Yes/No | N
-sask1 -sask_asequence | boolean | Ask for begin/end/reverse | Boolean value Yes/No | N
-snucleotide1 -snucleotide_asequence | boolean | Sequence is nucleotide | Boolean value Yes/No | N
-sprotein1 -sprotein_asequence | boolean | Sequence is protein | Boolean value Yes/No | N
-slower1 -slower_asequence | boolean | Make lower case | Boolean value Yes/No | N
-supper1 -supper_asequence | boolean | Make upper case | Boolean value Yes/No | N
-scircular1 -scircular_asequence | boolean | Sequence is circular | Boolean value Yes/No | N
-sformat1 -sformat_asequence | string | Input sequence format | Any string |
-iquery1 -iquery_asequence | string | Input query fields or ID list | Any string |
-ioffset1 -ioffset_asequence | integer | Input start position offset | Any integer value | 0
-sdbname1 -sdbname_asequence | string | Database name | Any string |
-sid1 -sid_asequence | string | Entryname | Any string |
-ufo1 -ufo_asequence | string | UFO features | Any string |
-fformat1 -fformat_asequence | string | Features format | Any string |
-fopenfile1 -fopenfile_asequence | string | Features file name | Any string |
"-bsequence" associated seqall qualifiers
-sbegin2 -sbegin_bsequence | integer | Start of each sequence to be used | Any integer value | 0
-send2 -send_bsequence | integer | End of each sequence to be used | Any integer value | 0
-sreverse2 -sreverse_bsequence | boolean | Reverse (if DNA) | Boolean value Yes/No | N
-sask2 -sask_bsequence | boolean | Ask for begin/end/reverse | Boolean value Yes/No | N
-snucleotide2 -snucleotide_bsequence | boolean | Sequence is nucleotide | Boolean value Yes/No | N
-sprotein2 -sprotein_bsequence | boolean | Sequence is protein | Boolean value Yes/No | N
-slower2 -slower_bsequence | boolean | Make lower case | Boolean value Yes/No | N
-supper2 -supper_bsequence | boolean | Make upper case | Boolean value Yes/No | N
-scircular2 -scircular_bsequence | boolean | Sequence is circular | Boolean value Yes/No | N
-sformat2 -sformat_bsequence | string | Input sequence format | Any string |
-iquery2 -iquery_bsequence | string | Input query fields or ID list | Any string |
-ioffset2 -ioffset_bsequence | integer | Input start position offset | Any integer value | 0
-sdbname2 -sdbname_bsequence | string | Database name | Any string |
-sid2 -sid_bsequence | string | Entryname | Any string |
-ufo2 -ufo_bsequence | string | UFO features | Any string |
-fformat2 -fformat_bsequence | string | Features format | Any string |
-fopenfile2 -fopenfile_bsequence | string | Features file name | Any string |
"-outfile" associated align qualifiers
-aformat3 -aformat_outfile | string | Alignment format | Any string | srspair
-aextension3 -aextension_outfile | string | File name extension | Any string |
-adirectory3 -adirectory_outfile | string | Output directory | Any string |
-aname3 -aname_outfile | string | Base file name | Any string |
-awidth3 -awidth_outfile | integer | Alignment width | Any integer value | 0
-aaccshow3 -aaccshow_outfile | boolean | Show accession number in the header | Boolean value Yes/No | N
-adesshow3 -adesshow_outfile | boolean | Show description in the header | Boolean value Yes/No | N
-ausashow3 -ausashow_outfile | boolean | Show the full USA in the alignment | Boolean value Yes/No | N
-aglobal3 -aglobal_outfile | boolean | Show the full sequence in alignment | Boolean value Yes/No | N
General qualifiers
-auto | boolean | Turn off prompts | Boolean value Yes/No | N
-stdout | boolean | Write first file to standard output | Boolean value Yes/No | N
-filter | boolean | Read first file from standard input, write first file to standard output | Boolean value Yes/No | N
-options | boolean | Prompt for standard and additional values | Boolean value Yes/No | N
-debug | boolean | Write debug output to program.dbg | Boolean value Yes/No | N
-verbose | boolean | Report some/full command line options | Boolean value Yes/No | Y
-help | boolean | Report command line options and exit. More information on associated and general qualifiers can be found with -help -verbose | Boolean value Yes/No | N
-warning | boolean | Report warnings | Boolean value Yes/No | Y
-error | boolean | Report errors | Boolean value Yes/No | Y
-fatal | boolean | Report fatal errors | Boolean value Yes/No | Y
-die | boolean | Report dying program messages | Boolean value Yes/No | Y
-version | boolean | Report version number and exit | Boolean value Yes/No | N

## Input file format

water reads a nucleotide or protein sequence and one or more sequence to be aligned to it.

The input is a standard EMBOSS sequence query (also known as a 'USA').

Major sequence database sources defined as standard in EMBOSS installations include srs:embl, srs:uniprot and ensembl

Data can also be read from sequence output in any supported format written by an EMBOSS or third-party application.

The input format can be specified by using the command-line qualifier `-sformat xxx`, where 'xxx' is replaced by the name of the required format. The available format names are: gff (gff3), gff2, embl (em), genbank (gb, refseq), ddbj, refseqp, pir (nbrf), swissprot (swiss, sw), dasgff and debug.

See: http://emboss.sf.net/docs/themes/SequenceFormats.html for further information on sequence formats.

### Input files for usage example

'tsw:hba_human' is a sequence entry in the example protein database 'tsw'

### Database entry: tsw:hba_human

    ID   HBA_HUMAN               Reviewed;         142 AA.
    AC   P69905; P01922; Q1HDT5; Q3MIF5; Q53F97; Q96KF1; Q9NYR7; Q9UCM0;
    DT   21-JUL-1986, integrated into UniProtKB/Swiss-Prot.
    DT   23-JAN-2007, sequence version 2.
    DT   13-JUN-2012, entry version 108.
    DE   RecName: Full=Hemoglobin subunit alpha;
    DE   AltName: Full=Alpha-globin;
    DE   AltName: Full=Hemoglobin alpha chain;
    GN   Name=HBA1;
    GN   and
    GN   Name=HBA2;
    OS   Homo sapiens (Human).
    OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
    OC   Mammalia; Eutheria; Euarchontoglires; Primates; Haplorrhini;
    OC   Catarrhini; Hominidae; Homo.
    OX   NCBI_TaxID=9606;
    RN   [1]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA] (HBA1).
    RX   MEDLINE=81088339; PubMed=7448866; DOI=10.1016/0092-8674(80)90347-5;
    RA   Michelson A.M., Orkin S.H.;
    RT   "The 3' untranslated regions of the duplicated human alpha-globin
    RT   genes are unexpectedly divergent.";
    RL   Cell 22:371-377(1980).
    RN   [2]
    RP   NUCLEOTIDE SEQUENCE [MRNA] (HBA2).
    RX   MEDLINE=80137531; PubMed=6244294;
    RA   Wilson J.T., Wilson L.B., Reddy V.B., Cavallesco C., Ghosh P.K.,
    RA   Deriel J.K., Forget B.G., Weissman S.M.;
    RT   "Nucleotide sequence of the coding portion of human alpha globin
    RT   messenger RNA.";
    RL   J. Biol. Chem. 255:2807-2815(1980).
    RN   [3]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA] (HBA2).
    RX   MEDLINE=81175088; PubMed=6452630; DOI=10.1073/pnas.77.12.7054;
    RA   Liebhaber S.A., Goossens M.J., Kan Y.W.;
    RT   "Cloning and complete nucleotide sequence of human 5'-alpha-globin
    RT   gene.";
    RL   Proc. Natl. Acad. Sci. U.S.A. 77:7054-7058(1980).
    RN   [4]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
    RX   PubMed=6946451; DOI=10.1073/pnas.78.8.5041;
    RA   Orkin S.H., Goff S.C., Hechtman R.L.;
    RT   "Mutation in an intervening sequence splice junction in man.";
    RL   Proc. Natl. Acad. Sci. U.S.A. 78:5041-5045(1981).
    RN   [5]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], AND VARIANT LYS-32.
    RX   MEDLINE=21303311; PubMed=11410421;
    RA   Zhao Y., Xu X.;
    RT   "Alpha2(CD31 AGG-->AAG, Arg-->Lys) causing non-deletional alpha-
    RT   thalassemia in a Chinese family with HbH disease.";

      [Part of this file has been deleted for brevity]

    FT                                /FTId=VAR_002841.
    FT   VARIANT     132    132       S -> P (in Questembert; highly unstable;
    FT                                causes alpha-thalassemia).
    FT                                /FTId=VAR_002843.
    FT   VARIANT     134    134       S -> R (in Val de Marne; O(2) affinity
    FT                                up).
    FT                                /FTId=VAR_002844.
    FT   VARIANT     136    136       V -> E (in Pavie).
    FT                                /FTId=VAR_002845.
    FT   VARIANT     137    137       L -> M (in Chicago).
    FT                                /FTId=VAR_002846.
    FT   VARIANT     137    137       L -> P (in Bibba; unstable; causes alpha-
    FT                                thalassemia).
    FT                                /FTId=VAR_002847.
    FT   VARIANT     137    137       L -> R (in Toyama).
    FT                                /FTId=VAR_035242.
    FT   VARIANT     139    139       S -> P (in Attleboro; O(2) affinity up).
    FT                                /FTId=VAR_002848.
    FT   VARIANT     140    140       K -> E (in Hanamaki; O(2) affinity up).
    FT                                /FTId=VAR_002849.
    FT   VARIANT     140    140       K -> T (in Tokoname; O(2) affinity up).
    FT                                /FTId=VAR_002850.
    FT   VARIANT     141    141       Y -> H (in Rouen/Ethiopia; O(2) affinity
    FT                                up).
    FT                                /FTId=VAR_002851.
    FT   VARIANT     142    142       R -> C (in Nunobiki; O(2) affinity up).
    FT                                /FTId=VAR_002852.
    FT   VARIANT     142    142       R -> H (in Suresnes; O(2) affinity up).
    FT                                /FTId=VAR_002854.
    FT   VARIANT     142    142       R -> L (in Legnano; O(2) affinity up).
    FT                                /FTId=VAR_002853.
    FT   VARIANT     142    142       R -> P (in Singapore).
    FT                                /FTId=VAR_002855.
    FT   CONFLICT     10     10       N -> H (in Ref. 13; BAD97112).
    FT   HELIX         5     16
    FT   HELIX        17     21
    FT   HELIX        22     36
    FT   HELIX        38     43
    FT   HELIX        54     72
    FT   HELIX        74     76
    FT   HELIX        77     80
    FT   HELIX        82     90
    FT   HELIX        97    113
    FT   TURN        115    117
    FT   HELIX       120    137
    FT   TURN        138    140
    SQ   SEQUENCE   142 AA;  15258 MW;  15E13666573BBBAE CRC64;
         MVLSPADKTN VKAAWGKVGA HAGEYGAEAL ERMFLSFPTT KTYFPHFDLS HGSAQVKGHG
         KKVADALTNA VAHVDDMPNA LSALSDLHAH KLRVDPVNFK LLSHCLLVTL AAHLPAEFTP
         AVHASLDKFL ASVSTVLTSK YR
    //

### Database entry: tsw:hbb_human

    ID   HBB_HUMAN               Reviewed;         147 AA.
    AC   P68871; A4GX73; B2ZUE0; P02023; Q13852; Q14481; Q14510; Q45KT0;
    AC   Q549N7; Q6FI08; Q6R7N2; Q8IZI1; Q9BX96; Q9UCD6; Q9UCP8; Q9UCP9;
    DT   21-JUL-1986, integrated into UniProtKB/Swiss-Prot.
    DT   23-JAN-2007, sequence version 2.
    DT   13-JUN-2012, entry version 108.
    DE   RecName: Full=Hemoglobin subunit beta;
    DE   AltName: Full=Beta-globin;
    DE   AltName: Full=Hemoglobin beta chain;
    DE   Contains:
    DE     RecName: Full=LVV-hemorphin-7;
    GN   Name=HBB;
    OS   Homo sapiens (Human).
    OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
    OC   Mammalia; Eutheria; Euarchontoglires; Primates; Haplorrhini;
    OC   Catarrhini; Hominidae; Homo.
    OX   NCBI_TaxID=9606;
    RN   [1]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
    RX   MEDLINE=77126403; PubMed=1019344;
    RA   Marotta C., Forget B., Cohen-Solal M., Weissman S.M.;
    RT   "Nucleotide sequence analysis of coding and noncoding regions of human
    RT   beta-globin mRNA.";
    RL   Prog. Nucleic Acid Res. Mol. Biol. 19:165-175(1976).
    RN   [2]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
    RX   MEDLINE=81064667; PubMed=6254664; DOI=10.1016/0092-8674(80)90428-6;
    RA   Lawn R.M., Efstratiadis A., O'Connell C., Maniatis T.;
    RT   "The nucleotide sequence of the human beta-globin gene.";
    RL   Cell 21:647-651(1980).
    RN   [3]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], AND VARIANT LYS-7.
    RX   PubMed=16175509; DOI=10.1086/491748;
    RA   Wood E.T., Stover D.A., Slatkin M., Nachman M.W., Hammer M.F.;
    RT   "The beta-globin recombinational hotspot reduces the effects of strong
    RT   selection around HbC, a recently arisen mutation providing resistance
    RT   to malaria.";
    RL   Am. J. Hum. Genet. 77:637-642(2005).
    RN   [4]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
    RA   Lu L., Hu Z.H., Du C.S., Fu Y.S.;
    RT   "DNA sequence of the human beta-globin gene isolated from a healthy
    RT   Chinese.";
    RL   Submitted (JUN-1997) to the EMBL/GenBank/DDBJ databases.
    RN   [5]
    RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], AND VARIANT ARG-113.
    RA   Cabeda J.M., Correia C., Estevinho A., Cardoso C., Amorim M.L.,
    RA   Cleto E., Vale L., Coimbra E., Pinho L., Justica B.;
    RT   "Unexpected patterns of globin mutations in thalassemia patients from
    RT   north of Portugal.";

      [Part of this file has been deleted for brevity]

    FT   VARIANT     141    141       A -> V (in Puttelange; polycythemia; O(2)
    FT                                affinity up).
    FT                                /FTId=VAR_003082.
    FT   VARIANT     142    142       L -> R (in Olmsted; unstable).
    FT                                /FTId=VAR_003083.
    FT   VARIANT     143    143       A -> D (in Ohio; O(2) affinity up).
    FT                                /FTId=VAR_003084.
    FT   VARIANT     144    144       H -> D (in Rancho Mirage).
    FT                                /FTId=VAR_003085.
    FT   VARIANT     144    144       H -> P (in Syracuse; O(2) affinity up).
    FT                                /FTId=VAR_003087.
    FT   VARIANT     144    144       H -> Q (in Little Rock; O(2) affinity
    FT                                up).
    FT                                /FTId=VAR_003086.
    FT   VARIANT     144    144       H -> R (in Abruzzo; O(2) affinity up).
    FT                                /FTId=VAR_003088.
    FT   VARIANT     145    145       K -> E (in Mito; O(2) affinity up).
    FT                                /FTId=VAR_003089.
    FT   VARIANT     146    146       Y -> C (in Rainier; O(2) affinity up).
    FT                                /FTId=VAR_003090.
    FT   VARIANT     146    146       Y -> H (in Bethesda; O(2) affinity up).
    FT                                /FTId=VAR_003091.
    FT   VARIANT     147    147       H -> D (in Hiroshima; O(2) affinity up).
    FT                                /FTId=VAR_003092.
    FT   VARIANT     147    147       H -> L (in Cowtown; O(2) affinity up).
    FT                                /FTId=VAR_003093.
    FT   VARIANT     147    147       H -> P (in York; O(2) affinity up).
    FT                                /FTId=VAR_003094.
    FT   VARIANT     147    147       H -> Q (in Kodaira; O(2) affinity up).
    FT                                /FTId=VAR_003095.
    FT   CONFLICT     26     26       Missing (in Ref. 15; ACD39349).
    FT   CONFLICT     42     42       F -> L (in Ref. 13; AAR96398).
    FT   HELIX         6     16
    FT   TURN         21     23
    FT   HELIX        24     35
    FT   HELIX        37     42
    FT   HELIX        44     46
    FT   HELIX        52     57
    FT   HELIX        59     77
    FT   TURN         78     80
    FT   HELIX        82     94
    FT   TURN         95     97
    FT   HELIX       102    119
    FT   HELIX       120    122
    FT   HELIX       125    142
    FT   HELIX       144    146
    SQ   SEQUENCE   147 AA;  15998 MW;  A31F6D621C6556A1 CRC64;
         MVHLTPEEKS AVTALWGKVN VDEVGGEALG RLLVVYPWTQ RFFESFGDLS TPDAVMGNPK
         VKAHGKKVLG AFSDGLAHLD NLKGTFATLS ELHCDKLHVD PENFRLLGNV LVCVLAHHFG
         KEFTPPVQAA YQKVVAGVAN ALAHKYH
    //

## Output file format

The output is a standard EMBOSS alignment file.

The results can be output in one of several styles by using the command-line qualifier `-aformat xxx`, where 'xxx' is replaced by the name of the required format. Some of the alignment formats can cope with an unlimited number of sequences, while others are only for pairs of sequences.

The available multiple alignment format names are: multiple, simple, fasta, msf, clustal, mega, meganon, nexus,, nexusnon, phylip, phylipnon, selex, treecon, tcoffee, debug, srs.

The available pairwise alignment format names are: pair, markx0, markx1, markx2, markx3, markx10, match, sam, bam, score, srspair

See: http://emboss.sf.net/docs/themes/AlignFormats.html for further information on alignment formats.

By default the output is in 'srspair' format.

### Output files for usage example

### File: hba_human.water

    ########################################
    # Program: water
    # Rundate: Sun 15 Jul 2012 12:00:00
    # Commandline: water
    #    [-asequence] tsw:hba_human
    #    [-bsequence] tsw:hbb_human
    # Align_format: srspair
    # Report_file: hba_human.water
    ########################################

    #=======================================
    #
    # Aligned_sequences: 2
    # 1: HBA_HUMAN
    # 2: HBB_HUMAN
    # Matrix: EBLOSUM62
    # Gap_penalty: 10.0
    # Extend_penalty: 0.5
    #
    # Length: 145
    # Identity:      63/145 (43.4%)
    # Similarity:    88/145 (60.7%)
    # Gaps:           8/145 ( 5.5%)
    # Score: 293.5
    #
    #
    #=======================================

    HBA_HUMAN          3 LSPADKTNVKAAWGKVGAHAGEYGAEALERMFLSFPTTKTYFPHF-DLS-     50
                         |:|.:|:.|.|.||||  :..|.|.|||.|:.:.:|.|:.:|..| |||
    HBB_HUMAN          4 LTPEEKSAVTALWGKV--NVDEVGGEALGRLLVVYPWTQRFFESFGDLST     51

    HBA_HUMAN         51 ----HGSAQVKGHGKKVADALTNAVAHVDDMPNALSALSDLHAHKLRVDP     96
                             .|:.:||.|||||..|.::.:||:|::....:.||:||..||.|||
    HBB_HUMAN         52 PDAVMGNPKVKAHGKKVLGAFSDGLAHLDNLKGTFATLSELHCDKLHVDP    101

    HBA_HUMAN         97 VNFKLLSHCLLVTLAAHLPAEFTPAVHASLDKFLASVSTVLTSKY    141
                         .||:||.:.|:..||.|...||||.|.|:..|.:|.|:..|..||
    HBB_HUMAN        102 ENFRLLGNVLVCVLAHHFGKEFTPPVQAAYQKVVAGVANALAHKY    146

    #---------------------------------------
    #---------------------------------------

The Identity: is the percentage of identical matches between the two sequences over the reported aligned region (including any gaps in the length).

The Similarity: is the percentage of matches between the two sequences over the reported aligned region (including any gaps in the length).

## Data files

For protein sequences EBLOSUM62 is used for the substitution matrix. For nucleotide sequence, EDNAFULL is used. Others can be specified.

EMBOSS data files are distributed with the application and stored in the standard EMBOSS data directory, which is defined by the EMBOSS environment variable EMBOSS_DATA.

To see the available EMBOSS data files, run:

    % embossdata -showall

To fetch one of the data files (for example 'Exxx.dat') into your current directory for you to inspect or modify, run:

    % embossdata -fetch -file Exxx.dat

Users can provide their own data files in their own directories. Project specific files can be put in the current directory, or for tidier directory listings in a subdirectory called ".embossdata". Files for all EMBOSS runs can be put in the user's home directory, or again in a subdirectory called ".embossdata".

The directories are searched in the following order:

- . (your current directory)
- .embossdata (under your current directory)
- ~/ (your home directory)
- ~/.embossdata

## Notes

A local alignment searches for regions of local similarity between two sequences and need not include the entire length of the sequences. Local alignment methods are very useful for scanning databases or other circumsatnces when you wish to find matches between small regions of sequences, for example between protein domains.

## References

1. Smith TF, Waterman MS (1981) J. Mol. Biol 147(1);195-7

## Warnings

Local alignment methods only report the best matching areas between two sequences - there may be a large number of alternative local alignments that do not score as highly. If two proteins share more than one common region, for example one has a single copy of a particular domain while the other has two copies, it may be possible to "miss" the second and subsequent alignments. You will be able to see this situation if you have done a dotplot and your local alignment does not show all the features you expected to see.

water is for aligning the best matching subsequences of two sequences. It does not necessarily align whole sequences against each other; you should use needle if you wish to align closely related sequences along their whole lengths.

A true Smith Waterman implementation like water needs memory proportional to the product of the sequence lengths. For two sequences of length 10,000,000 and 1,000 it therefore needs memory proportional to 10,000,000,000 characters. Two arrays of this size are produced, one of ints and one of floats so multiply that figure by 8 to get the memory usage in bytes. That doesn't include other overheads. Therefore only use water and needle for accurate alignment of reasonably short sequences. It should not be used with very large sequences unless you have a lot of memory and a lot of time. If you run out of memory, try using supermatcher or matcher instead.

## Diagnostic Error Messages

    Uncaught exception
     Assertion failed
     raised at ajmem.c:xxx

Probably means you have run out of memory. Try using supermatcher or matcher if this happens.

## Exit status

0 if successful.

## Known bugs

None.

## See also

Program name | Description
--- | ---
matcher | Waterman-Eggert local alignment of two sequences
seqmatchall | All-against-all word comparison of a sequence set
supermatcher | Calculate approximate local pair-wise alignments of larger sequences
wordfinder | Match large sequences against one or more other sequences
wordmatch | Find regions of identity (exact matches) of two sequences

matcher is a local alignment program that gives as good an alignment as water but it uses far less memory. However, water runs twice as fast as matcher.

supermatcher is designed for local alignments of very large sequences. It gives good results as long as there is not a significant amount of insertion or deletion in the alignment.

## Author(s)

Alan Bleasby
European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, UK

Please report all bugs to the EMBOSS bug team (emboss-bug © emboss.open-bio.org) not to the original author.

## History

Completed 7th July 1999.

Modified 27th July 1999 - tweaking scoring.

Modified 22 Oct 2000 - added ID and Similarity scores.

## Target users

This program is intended to be used by everyone and everything, from naive users to embedded scripts.

## Comments

None