FASTA/SSEARCH/[T]FASTX/Y/LALIGN

Index

NAME

DESCRIPTION

Running the FASTA programs

FASTA program options

Option summary:

Reading sequences from STDIN

Environment variables:

AUTHOR

NAME

DESCRIPTION

Release 3.5 of the FASTA package provides a modular set of sequence comparison programs that can run on conventional single processor computers or in parallel on multiprocessor computers. More than a dozen programs - fasta35, fastx35/tfastx35, fasty35/tfasty35, fasts35/tfasts35, fastm35, fastf35/tfastf35, ssearch35, ggsearch35, and glsearch35 - are currently available.

All of the comparison programs share a set of basic command line options; additional options are available for individual comparison functions.

Threaded versions of the FASTA programs (fasta35_t, ssearch35_t, etc.) will run in parallel on modern Linux and Unix multi-core or multi-processor computers. Accelerated versions of the Smith-Waterman algorithm are available for architectures with the Intel SSE2 or Altivec PowerPC architectures, which can speed-up Smith-Waterman calculations 10 - 20-fold.

In addition to the serial and threaded versions of the FASTA programs, PVM and MPI parallel versions are available as pv35compfa, mp35compfaf, pv35compsw, mp35compsw, etc. For more information, see pvcomp.1, readme.pvm_mpi. The PVM/MPI program versions use same command line options as the serial and threaded FASTA program versions.

Running the FASTA programs

Although the FASTA programs can be run interactively, prompting for a query file and a library, it is usually more convenient to run them from the Unix, MacOSX terminal, or Windows shell command line. Thus,

      fasta35_t -q -option1 -option2 -option3 query.file library.file > fasta.output

runs the threaded version of fasta35 program, without asking for any input (-q), setting various parameter and output options, comparing the sequences in query.file to the sequences in library.file. Optional arguments to the FASTA programs must precede the query.file, library.file, and optional ktup arguments. The FASTA program provides an option (-O) for sending output to a file, but generally it is better to simply redirect output with the ">" shell symbol.

FASTA program options

The default scoring matrix and gap penalties used by each of the programs have been selected for high sensitivity searches with the various algorithms. The default program behavior can be modified by providing command line options before the query.file and library.file arguments. Command line options can also be used in interactive mode.

Command line arguments come in several classes.

(1) Commands that specify the comparison type. FASTA, FASTS, FASTM, SSEARCH, GGSEARCH, and GLSEARCH can compare either protein or DNA sequences, and attempt to recognize the comparison type by looking the residue composition. -n, -p specify DNA (nucleotide) or protein comparison, respectively. -U specifies RNA comparison.

(2) Commands that limit the set of sequences compared: -1, -3, -M.

(3) Commands that modify the scoring parameters: -f gap-open penaltyP, -g gap-extend penalty, -h inter-codon frame-shift, -j within-codon frame-shift, -s scoring-matrix, -r match/mismatch score, -x X:X score.

(4) Commands that modify the algorithm (mostly FASTA and [T]FASTX/Y): -c, -w, -y, -o. The -S can be used to ignore lower-case (low complexity) residues during the initial score calculation.

(5) Commands that modify the output: -A, -b number, -C width, -d number, -L, -m 0-11, -w line-width, -W context-width, -X offset1,ofset2

(6) Commands that affect statistical estimates: -Z, -k.

Option summary:

-1

Sort by "init1" score (obsolete)

-3

(TFASTX/Y35 only) use only forward frame translations

-a #

"SHOWALL" option attempts to align all of both sequences in FASTA and SSEARCH.

-A

(FASTA35 DNA comparison only) force Smith-Waterman alignment for output. Smith-Waterman is the default for FASTA protein alignment and [T]FASTX/Y, but not for DNA comparisons with FASTA.

-b #

number of best scores to show (must be < expectation cutoff if -E is given). By default, this option is no longer used; all scores better than the expectation (E()) cutoff are listed.

-B

show z-scores rather than bit scores (for compatibility with much older versions).

-c #

threshold for band optimization (FASTA, [T]FASTX/Y)

-C #

length of name abbreviation in alignments, default = 6. Must be less than 20.

-d #

number of best alignments to show ( must be < expectation (-E) cutoff)

-D

turn on debugging mode. Enables checks on sequence alphabet that cause problems with tfastx35, tfasty35 (only available after compile time option).

-E #

expectation value upper limit for score and alignment display. Defaults are 10.0 for FASTA35 and SSEARCH35 protein searches, 5.0 for translated DNA/protein comparisons, and 2.0 for DNA/DNA searches.

-f #

penalty for opening a gap.

-F #

expectation value lower limit for score and alignment display. -F 1e-6 prevents library sequences with E()-values lower than 1e-6 from being displayed. Use to shift focus to more distant relationships.

-g #

penalty for additional residues in a gap

-h #

([T]FASTX/Y only) penalty for a frameshift between two codons.

-j #

([T]FASTY only) penalty for a frameshift within a codon.

-H

turn off histogram display. (The meaning of -H is reversed with the PVM/MPI parallel versions, where the histogram display is off by default).

-i

(FASTA DNA, [T]FASTX/Y) compare against only the reverse complement of the library sequence.

-k

specify number of shuffles for statistical parameter estimation (default=500).

-l str

specify FASTLIBS file

-L

report long sequence description in alignments (up to 200 characters).

-m 0,1,2,3,4,5,6,9,10,11

alignment display options. -m 0, 1, 2, 3 display different types of alignments. -m 4 provides an alignment "map" on the query. -m 5 combines the alignment map and a -m 0 alignment. -m 6 provides an HTML output.

-m 9

does not change the alignment output, but provides alignment coordinate and percent identity information with the best scores report. -m 9c adds encoded alignment information to the -m 9; -m 9i provides only percent identity and alignment length information with the best scores. With current versions of the FASTA programs, independent -m options can be combined; e.g. -m 1 -m 9c -m 6.

-m 11

provide lav format output from lalign35. It does not currently affect other alignment algorithms. The lav2ps and lav2svg programs can be used to convert lav format output to postscript/SVG alignment "dot-plots".

-M #-#

molecular weight (residue) cutoffs. -M "101-200" examines only sequences that are 101-200 residues long.

-n

force query to nucleotide sequence

-N #

break long library sequences into blocks of # residues. Useful for bacterial genomes, which have only one sequence entry. -N 2000 works well for well for bacterial genomes.

-o

(FASTA) turn fasta band optimization off during initial phase. This was the behavior of fasta1.x versions (obsolete).

-O file

send output to file.

-p

Force query sequence type to protein.

-P "file type"

specify a PSI-BLAST PSSM file of type "type". Available types are:

0 - ascii PSSM file, produced by blastpgp -Q file.pssm 1 - binary (architecture dependent) PSSM file, produced by blastpgp -C file.pssm -u 0 2 - binary ASN.1 (architecture independent) PSSM file, produced by blastpgp -C file.pssm -u 2

-q/-Q

quiet option; do not prompt for input

-r "+n/-m"

(DNA only) values for match/mismatch for DNA comparisons. +n is used for the maximum positive value and -m is used for the maximum negative value. Values between max and min, are rescaled, but residue pairs having the value -1 continue to be -1.

-R file

save all scores to statistics file (previously -r file)

-s name

specify substitution matrix. BLOSUM50 is used by default; PAM250, PAM120, and BLOSUM62 can be specified by setting -s P120, P250, or BL62. With this version, many more scoring matrices are available, including BLOSUM80 (BL80), and MDM10, MDM20, MDM40 (Jones, Taylor, and Thornton, 1992 CABIOS 8:275-282; specified as -s M10, -s M20, -s M40). Alternatively, BLASTP1.4 format scoring matrix files can be specified. BL80, BL62, and P120 are scaled in 1/2 bit units; all the other matrices use 1/3 bit units. DNA scoring matrices can also be specified with the "-r" option.

-S

treat lower case letters in the query or database as low complexity regions that are equivalent to 'X' during the initial database scan, but are treated as normal residues for the final alignment display. Statistical estimates are based on the 'X'ed out sequence used during the initial search. Protein databases (and query sequences) can be generated in the appropriate format using John Wooton's "pseg" program, available from ftp://ncbi.nlm.nih.gov/pub/seg/pseg. Once you have compiled the "pseg" program, use the command:

  pseg database.fasta -z 1 -q > database.lc_seg

-t #

Translation table - [t]fastx35 and [t]fasty35 support the BLAST tranlation tables. See the NCBI Genetic Code site. In addition, you can score for the end of a protein match with '-t -t' which will add "*" to the end of your query sequences (but your protein library sequences must also have '*'). Built in protein matrices know about '*:*' matches; if you want to use '-t t' with your own matrix, you will need to include '*' in the matrix.

-T #

(threaded, parallel only) number of threads or workers to use (set by default to 4 at compile time).

-U

Do RNA sequence comparisons: treat 'T' as 'U', allow G:U base pairs (by scoring "G-A" and "T-C" as "G-G" -1). Search only one strand.

-V "?$%*"

Allow special annotation characters in query sequence. These characters will be displayed in the alignments on the coordinate number line.

-w #

line width for similarity score, sequence alignment, output.

-W #

context length (default is 1/2 of line width -w) for programs, like fasta and ssearch, that provide additional sequence context.

-x #match,#mismatch

scores used for matches to 'X:X','N:N', '*:*' matches, and the corresponding specified in the scoring matrix. If only one value is given, it is used for both values.

-X "#,#"

offsets query, library sequence for numbering alignments

-y #

Width for band optimization; by default 16 for DNA and protein ktup=2; 32 for protein ktup=1;

-z #

Specify statistical calculation. Default is -z 1 for local similarity searches, which uses regression against the length of the library sequence. -z -1 disables statistics. -z 0 estimates significance without normalizing for sequence length. -z 2 provides maximum likelihood estimates for lambda and K, censoring the 250 lowest and 250 highest scores. -z 3 uses Altschul and Gish's statistical estimates for specific protein BLOSUM scoring matrices and gap penalties. -z 4,5: an alternate regression method. -z 6 uses a composition based maximum likelihood estimate based on the method of Mott (1992) Bull. Math. Biol. 54:59-75. -z 11,12,14,15,16: compute the regression against scores of randomly shuffled copies of the library sequences. Twice as many comparisons are performed, but accurate estimates can be generated from databases of related sequences. -z 11 uses the -z 1 regression strategy, etc.

-Z db_size

Set the apparent database size used for expectation value calculations (used for protein/protein FASTA and SSEARCH, and for [T]FASTX/Y).

Reading sequences from STDIN

      cat query.aa | fasta35 -q @:50-150 s

would search the 's' database with residues 50-150 of query.aa. FASTA cannot automatically detect the sequence type (protein vs DNA) when "stdin" is used and assumes protein comparisons by default; the '-n' option is required for DNA for STDIN queries.

Environment variables:

FASTLIBS

location of library choice file (-l FASTLIBS)

SMATRIX

default scoring matrix (-s SMATRIX)

SRCH_URL

the format string used to define the option to re-search the database.

REF_URL

the format string used to define the option to lookup the library sequence in entrez, or some other database.

AUTHOR