FASTA (Ligand Gated Ion Channel Protein Databases)


FASTA (pronounced FAST-AYE) is a suite of programs for searching nucleotide or protein databases with a query sequence. FASTA itself performs a local heuristic search of a protein or nucleotide database for a query of the same type. FASTX and FASTY translate a nucleotide query for searching a protein database. TFASTX and TFASTY translate a nucleotide database to be searched with a protein query. Optimal searches are available with the programs SSEARCH (local), GGSEARCH (global) and GLSEARCH (global query against local database).

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How to use this tool

Running a tool from the web form is a simple multiple steps process, starting at the top of the page and following the steps to the bottom.

Each tool has at least 2 steps, but most of them have more:

  • The first steps are usually where the user sets the tool input (e.g. sequences, databases...)
  • In the following steps, the user has the possibility to change the default tool parameters
  • And finally, the last step is always the tool submission step, where the user can specify a title to be associated with the results and an email address for email notification. Using the submit button will effectively submit the information specified previously in the form to launch the tool on the server

Note that the parameters are validated prior to launching the tool on the server and in the event of a missing or wrong combination of parameters, the user will be notified directly in the form.

Step 1 - Database


The databases to run the sequence similarity search against. Multiple databases can be used at the same time

Database Name Description Abbreviation
LGICdb Protein Protein sequence similarity searching against the Ligand Gated Ion Channel Database lgicp

Default value is: LGICdb Protein [lgicp]

Step 2 - Sequence

Sequence Input Window

The query sequence can be entered directly into this form. The sequence can be be in GCG, FASTA, EMBL, GenBank, PIR, NBRF, PHYLIP or UniProtKB/Swiss-Prot format. A partially formatted sequence is not accepted. Adding a return to the end of the sequence may help certain applications understand the input. Note that directly using data from word processors may yield unpredictable results as hidden/control characters may be present.

Sequence File Upload

A file containing a valid sequence in any format (GCG, FASTA, EMBL, GenBank, PIR, NBRF, PHYLIP or UniProtKB/Swiss-Prot) can be used as input for the sequence similarity search. Word processors files may yield unpredictable results as hidden/control characters may be present in the files. It is best to save files with the Unix format option to avoid hidden Windows characters.

Sequence Type

Indicates if the query sequence is protein, DNA or RNA. Used to force FASTA to interpret the input sequence as specified type of sequence (via. the '-p', '-n' or '-U' options), this prevents issues when using nucleotide sequences that contain many ambiguous residues.

Type Abbreviation
PROTEIN protein
DNA dna
RNA rna

Default value is: PROTEIN [protein]

Step 3 - Parameters


The FASTA program to be used for the Sequence Similarity Search

Program Name Description Abbreviation
FASTA Scan a protein or DNA sequence library for similar sequences. fasta
FASTX Compare a DNA sequence to a protein sequence database, comparing the translated DNA sequence in forward and reverse frames. fastx
FASTY Compare a DNA sequence to a protein sequence database, comparing the translated DNA sequence in forward and reverse frames. fasty
SSEARCH Compare a protein or DNA sequence to a sequence database using the Smith-Waterman algorithm. ssearch

Default value is: FASTA [fasta]


(Protein searches) The substitution matrix used for scoring alignments when searching the database. Target identity is the average alignment identity the matrix would produce in the absence of homology and can be used to compare different matrix types. Alignment boundaries are more accurate when the alignment identity matches the target identity percentage.

Matrix Name Target Identity Abbreviation
BLOSUM50 25% BL50
BLASTP62 30% BP62
BLOSUM80 40% BL80
PAM250 20% P250
PAM120 35% P120
MDM40 65% M40
MDM20 85% M20
MDM10 90% M10
VTML160 25% VT160
VTML120 35% VT120
VTML80 40% VT80
VTML40 65% VT40
VTML20 85% VT20
VTML10 90% VT10

Default value is: BLOSUM50 [BL50]

Additional information


(Nucleotide searches) The match score is the bonus to the alignment score when matching the same base. The mismatch is the penalty when failing to match.

Match/mismatch_scores Abbreviation
N/A none

Gap Open Penalty

Score for the first residue in a gap.

Default value is: -10

Additional information

Gap Extend Penalty

Score for each additional residue in a gap.

Default value is: -2

Additional information


FASTA uses a rapid word-based lookup strategy to speed the initial phase of the similarity search. The KTUP is used to control the sensitivity of the search. Lower values lead to more sensitive, but slower searches.

Expectation Upper Limit

Limits the number of scores and alignments reported based on the expectation value. This is the maximum number of times the match is expected to occur by chance.

Default value is: 10

Expectation Lower Limit

Limit the number of scores and alignments reported based on the expectation value. This is the minimum number of times the match is expected to occur by chance. This allows closely related matches to be excluded from the result in favor of more distant relationships.

Default value is: 0 (default) [0]


For nucleotide sequences specify the sequence strand to be used for the search. By default both upper (provided) and lower (reverse complement of provided) strands are used, for single stranded sequences searching with only the upper or lower strand may provide better results.


Default value is: N/A [none]


Turn on/off the histogram in the FASTA result. The histogram gives a qualitative view of how well the statistical theory fits the similarity scores calculated by the program.

Default value is: no [false]


Filter regions of low sequence complexity. This can avoid issues with low complexity sequences where matches are found due to composition rather then meaningful sequence similarity. However in some cases filtering also masks regions of interest and so should be used with caution.

Value Description
none No filtering of the query sequence.

Default value is: none

Statistical Estimates

The statistical routines assume that the library contains a large sample of unrelated sequences. Options to select what method to use include regression, maximum likelihood estimates, shuffles, or combinations of these.

Name Description Value
Regress Uses a weighted regression of average score vs library sequence length. 1

Default value is: Regress [1]


Maximum number of match score summaries reported in the result output.

Default value is: 50


Maximum number of match alignments reported in the result output.

Default value is: 50

Sequence Range

Specify a range or section of the input sequence to use in the search. Example: Specifying '34-89' in an input sequence of total length 100, will tell FASTA to only use residues 34 to 89, inclusive.

Default value is: START-END

Database Range

Specify the sizes of the sequences in a database to search against. For example: 100-250 will search all sequences in a database with length between 100 and 250 residues, inclusive.

Default value is: START-END


Turn on/off the display of all significant alignments between query and library sequence.

Default value is: no [false]

Score Format

Different score report formats.

Name Description Value
Default Default FASTA score format default
-m 9 -- with coordinates scores and %identity To extend scores report with coordinates scores and %identity. 9
-m 9C -- with CIGAR alignment To display an alignment code in CIGAR format. 9C
-m 9c -- with encoded alignment To extend scores report with coordinate, %identity and encoded alignment details. 9c
-m 9i -- with identity and length To extend scores report with %identity and length only. 9i

Default value is: Default [default]

Translation Table

Query Genetic code to use in translation

Name Value
N/A -1
Standard SGC0 1
Vertebrate Mitochondrial 2
Yeast Mitochondrial 3
Mold Mitochondrial Protozoan Mitochondrial Coelenterate 4
Invertebrate Mitochondrial 5
Ciliate Nuclear Dasycladacean Nuclear Hexamita Nuclear 6
Echinoderm Mitochondrial Flatworm Mitochondrial 9
Euplotid Nuclear 10
Bacterial and Plant Plastid 11
Alternative Yeast Nuclear 12
Ascidian Mitochondrial 13
Alternative Flatworm Mitochondrial 14
Blepharisma Macronuclear 15
Chlorophycean Mitochondrial 16
Trematode Mitochondrial 21
Scenedesmus obliquus Mitochondrial 22
Thraustochytrium Mitochondrial 23

Default value is: Standard SGC0 [1]

Annotation Features

Turn on/off annotation features. Annotation features shows features from UniProtKB, such as variants, active sites, phospho-sites and binding sites that have been found in the aligned region of the database hit. To see the annotation features in the results after this has been enabled, select sequences of interest and click to 'Show' Alignments. This option also enables a new result tab (Domain Diagrams) that highlights domain regions.

Step 4 - Submission

Job title

It's possible to identify the tool result by giving it a name. This name will be associated to the results and might appear in some of the graphical representations of the results.

Email Notification

Running a tool is usually an interactive process, the results are delivered directly to the browser when they become available. Depending on the tool and its input parameters, this may take quite a long time. It's possible to be notified by email when the job is finished by simply ticking the box "Be notified by email". An email with a link to the results will be sent to the email address specified in the corresponding text box. Email notifications require valid email addresses.

Email Address

If email notification is requested, then a valid Internet email address in the form must be provided. This is not required when running the tool interactively (The results will be delivered to the browser window when they are ready).


Searching protein sequence libraries: comparison of the sensitivity and selectivity of the Smith-Waterman and FASTA algorithms.
(1991 Nov) Genomics 11 (3) :635-50
Rapid and sensitive sequence comparison with FASTP and FASTA.
(1990) Methods in enzymology 183 :63-98
Improved tools for biological sequence comparison.
(1988 Apr) Proceedings of the National Academy of Sciences of the United States of America 85 (8) :2444-8
A new bioinformatics analysis tools framework at EMBL-EBI.
(2010 Jul) Nucleic acids research 38 (Web Server issue) :W695-9
Analysis Tool Web Services from the EMBL-EBI.
(2013 Jul) Nucleic acids research 41 (Web Server issue) :W597-600

Contact details


For Support on this service: Please contact EMBL-EBI support at

The Author:

William R. Pearson (email:
Department of Biochemistry
Box 440, Jordan Hall
U. of Virginia
Charlottesville, VA