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hmmbuild(1) HMMER Manual hmmbuild(1)


hmmbuild - construct profiles from multiple sequence alignments


hmmbuild [options] hmmfile msafile


For each multiple sequence alignment in msafile build a profile HMM and save it to a new file hmmfile.

msafile may be '-' (dash), which means reading this input from stdin rather than a file.

hmmfile may not be '-' (stdout), because sending the HMM file to stdout would conflict with the other text output of the program.


Help; print a brief reminder of command line usage and all available options.

Name the new profile <s>. The default is to use the name of the alignment (if one is present in the msafile, or, failing that, the name of the hmmfile. If msafile contains more than one alignment, -n doesn't work, and every alignment must have a name annotated in the msafile (as in Stockholm #=GF ID annotation).

Direct the summary output to file <f>, rather than to stdout.

After each model is constructed, resave annotated, possibly modified source alignments to a file <f> in Stockholm format. The alignments are annotated with a reference annotation line indicating which columns were assigned as consensus, and sequences are annotated with what relative sequence weights were assigned. Some residues of the alignment may have been shifted to accommodate restrictions of the Plan7 profile architecture, which disallows transitions between insert and delete states.


Assert that sequences in msafile are protein, bypassing alphabet autodetection.

Assert that sequences in msafile are DNA, bypassing alphabet autodetection.

Assert that sequences in msafile are RNA, bypassing alphabet autodetection.


These options control how consensus columns are defined in an alignment.

Define consensus columns as those that have a fraction >= symfrac of residues as opposed to gaps. (See below for the --symfrac option.) This is the default.

Define consensus columns in next profile using reference annotation to the multiple alignment. This allows you to define any consensus columns you like.

Define the residue fraction threshold necessary to define a consensus column when using the --fast option. The default is 0.5. The symbol fraction in each column is calculated after taking relative sequence weighting into account, and ignoring gap characters corresponding to ends of sequence fragments (as opposed to internal insertions/deletions). Setting this to 0.0 means that every alignment column will be assigned as consensus, which may be useful in some cases. Setting it to 1.0 means that only columns that include 0 gaps (internal insertions/deletions) will be assigned as consensus.

We only want to count terminal gaps as deletions if the aligned sequence is known to be full-length, not if it is a fragment (for instance, because only part of it was sequenced). HMMER uses a simple rule to infer fragments: if the range of a sequence in the alignment (the number of alignment columns between the first and last positions of the sequence) is less than or equal to a fraction <x> times the alignment length in columns, then the sequence is handled as a fragment. The default is 0.5. Setting --fragthresh 0 will define no (nonempty) sequence as a fragment; you might want to do this if you know you've got a carefully curated alignment of full-length sequences. Setting --fragthresh 1 will define all sequences as fragments; you might want to do this if you know your alignment is entirely composed of fragments, such as translated short reads in metagenomic shotgun data.


HMMER uses an ad hoc sequence weighting algorithm to downweight closely related sequences and upweight distantly related ones. This has the effect of making models less biased by uneven phylogenetic representation. For example, two identical sequences would typically each receive half the weight that one sequence would. These options control which algorithm gets used.

Use the Henikoff position-based sequence weighting scheme [Henikoff and Henikoff, J. Mol. Biol. 243:574, 1994]. This is the default.

Use the Gerstein/Sonnhammer/Chothia weighting algorithm [Gerstein et al, J. Mol. Biol. 235:1067, 1994].

Use the same clustering scheme that was used to weight data in calculating BLOSUM substitution matrices [Henikoff and Henikoff, Proc. Natl. Acad. Sci 89:10915, 1992]. Sequences are single-linkage clustered at an identity threshold (default 0.62; see --wid) and within each cluster of c sequences, each sequence gets relative weight 1/c.

No relative weights. All sequences are assigned uniform weight.

Sets the identity threshold used by single-linkage clustering when using --wblosum. Invalid with any other weighting scheme. Default is 0.62.


After relative weights are determined, they are normalized to sum to a total effective sequence number, eff_nseq. This number may be the actual number of sequences in the alignment, but it is almost always smaller than that. The default entropy weighting method (--eent) reduces the effective sequence number to reduce the information content (relative entropy, or average expected score on true homologs) per consensus position. The target relative entropy is controlled by a two-parameter function, where the two parameters are settable with --ere and --esigma.

Adjust effective sequence number to achieve a specific relative entropy per position (see --ere). This is the default.

Set effective sequence number to the number of single-linkage clusters at a specific identity threshold (see --eid). This option is not recommended; it's for experiments evaluating how much better --eent is.

Turn off effective sequence number determination and just use the actual number of sequences. One reason you might want to do this is to try to maximize the relative entropy/position of your model, which may be useful for short models.

Explicitly set the effective sequence number for all models to <x>.

Set the minimum relative entropy/position target to <x>. Requires --eent. Default depends on the sequence alphabet. For protein sequences, it is 0.59 bits/position; for nucleotide sequences, it is 0.45 bits/position.

Sets the minimum relative entropy contributed by an entire model alignment, over its whole length. This has the effect of making short models have higher relative entropy per position than --ere alone would give. The default is 45.0 bits.

Sets the fractional pairwise identity cutoff used by single linkage clustering with the --eclust option. The default is 0.62.


By default, weighted counts are converted to mean posterior probability parameter estimates using mixture Dirichlet priors. Default mixture Dirichlet prior parameters for protein models and for nucleic acid (RNA and DNA) models are built in. The following options allow you to override the default priors.

Don't use any priors. Probability parameters will simply be the observed frequencies, after relative sequence weighting.

Use a Laplace +1 prior in place of the default mixture Dirichlet prior.


By default, if a query is a single sequence from a file in fasta format, hmmbuild constructs a search model from that sequence and a standard 20x20 substitution matrix for residue probabilities, along with two additional parameters for position-independent gap open and gap extend probabilities. These options allow the default single-sequence scoring parameters to be changed, and for single-sequence scoring options to be applied to a single sequence coming from an aligned format.

If a single sequence query comes from a multiple sequence alignment file, such as in stockholm format, the search model is by default constructed as is typically done for multiple sequence alignments. This option forces hmmbuild to use the single-sequence method with substitution score matrix.

Obtain residue alignment probabilities from the built-in substitution matrix named <s>. Several standard matrices are built-in, and do not need to be read from files. The matrix name <s> can be PAM30, PAM70, PAM120, PAM240, BLOSUM45, BLOSUM50, BLOSUM62, BLOSUM80, BLOSUM90, or DNA1. Only one of the --mx and --mxfile options may be used.

Obtain residue alignment probabilities from the substitution matrix in file <mxfile>. The default score matrix is BLOSUM62 for protein sequences, and DNA1 for nucleotide sequences (these matrices are internal to HMMER and do not need to be available as a file). The format of a substitution matrix <mxfile> is the standard format accepted by BLAST, FASTA, and other sequence analysis software. See for example files. (The only exception: we require matrices to be square, so for DNA, use files like NCBI's NUC.4.4, not NUC.4.2.)

Set the gap open probability for a single sequence query model to <x>. The default is 0.02. <x> must be >= 0 and < 0.5.

Set the gap extend probability for a single sequence query model to <x>. The default is 0.4. <x> must be >= 0 and < 1.0.


The location parameters for the expected score distributions for MSV filter scores, Viterbi filter scores, and Forward scores require three short random sequence simulations.

Sets the sequence length in simulation that estimates the location parameter mu for MSV filter E-values. Default is 200.

Sets the number of sequences in simulation that estimates the location parameter mu for MSV filter E-values. Default is 200.

Sets the sequence length in simulation that estimates the location parameter mu for Viterbi filter E-values. Default is 200.

Sets the number of sequences in simulation that estimates the location parameter mu for Viterbi filter E-values. Default is 200.

Sets the sequence length in simulation that estimates the location parameter tau for Forward E-values. Default is 100.

Sets the number of sequences in simulation that estimates the location parameter tau for Forward E-values. Default is 200.

Sets the tail mass fraction to fit in the simulation that estimates the location parameter tau for Forward evalues. Default is 0.04.


Set the number of parallel worker threads to <n>. On multicore machines, the default is 2. You can also control this number by setting an environment variable, HMMER_NCPU. There is also a master thread, so the actual number of threads that HMMER spawns is <n>+1.

This option is not available if HMMER was compiled with POSIX threads support turned off.

Assert that input msafile is in alignment format <s>, bypassing format autodetection. Common choices for <s> include: stockholm, a2m, afa, psiblast, clustal, phylip. For more information, and for codes for some less common formats, see main documentation. The string <s> is case-insensitive (a2m or A2M both work).

Seed the random number generator with <n>, an integer >= 0. If <n> is nonzero, any stochastic simulations will be reproducible; the same command will give the same results. If <n> is 0, the random number generator is seeded arbitrarily, and stochastic simulations will vary from run to run of the same command. The default seed is 42.

Window length tail mass. The upper bound, W, on the length at which nhmmer expects to find an instance of the model is set such that the fraction of all sequences generated by the model with length >= W is less than <x>. The default is 1e-7.

Override the model instance length upper bound, W, which is otherwise controlled by --w_beta. It should be larger than the model length. The value of W is used deep in the acceleration pipeline, and modest changes are not expected to impact results (though larger values of W do lead to longer run time).

Run as a parallel MPI program. Each alignment is assigned to a MPI worker node for construction. (Therefore, the maximum parallelization cannot exceed the number of alignments in the input msafile.) This is useful when building large profile libraries. This option is only available if optional MPI capability was enabled at compile-time.

For debugging MPI parallelization: arrest program execution immediately after start, and wait for a debugger to attach to the running process and release the arrest.

Restrict insert length parameterization such that the expected insert length at each position of the model is no more than <n>.


See hmmer(1) for a master man page with a list of all the individual man pages for programs in the HMMER package.

For complete documentation, see the user guide that came with your HMMER distribution (Userguide.pdf); or see the HMMER web page (


Copyright (C) 2023 Howard Hughes Medical Institute.
Freely distributed under the BSD open source license.

For additional information on copyright and licensing, see the file called COPYRIGHT in your HMMER source distribution, or see the HMMER web page (


Aug 2023 HMMER 3.4