ProtGenIQ (Random protein sequence generator)
Generate random protein sequences with controlled length, amino acid composition, and motifs.
Input
How to generate random protein sequences
Set a length range and an amino acid pool, then generate protein sequences in FASTA format. Each record gets a randomly chosen length within the inclusive range. The random positions sample uniformly from the selected pool. Copy the result or download it as a .fasta file.
For two records with both length bounds set to 12, Mixed composition, and start methionine enabled, a verified run produced:
>Random_Protein_1 length=12
MEYRAVDCGHWY
>Random_Protein_2 length=12
MMFQDNCDLTYFEvery run samples new residues. These are example outputs, not sequences that will repeat with the same settings.
Adding a motif
Motifs occupy positions within the requested length. With a fixed length of 12, Aromatic composition, start methionine enabled, and a C-terminal His-tag, a verified run returned:
>Random_Protein_1 length=12
MFWWFWHHHHHHThe first residue is the requested M, the five random residues come from F/Y/W, and the final six residues are the His-tag. Fixed motifs and a starting M can contain residues outside the selected random pool.
Input and settings
No existing sequence or upload is required. Counts and length bounds must be positive whole numbers, and the minimum length cannot exceed the maximum. The minimum must also fit the complete motif and any separate start methionine; impossible combinations return an error.
| Setting | Behavior | Default |
|---|---|---|
Number of sequences | Number of separate FASTA records. At least 1. | 1 |
Minimum length (aa) | Lower inclusive bound on the final sequence length, including fixed residues. At least 1. | 50 |
Maximum length (aa) | Upper inclusive bound on the final sequence length. Set equal to the minimum for a fixed length. | 100 |
Amino acid composition | Selects the random residue pool: mixed, hydrophobic, polar, charged, small, or aromatic. The pools are listed below. | mixed |
Include start methionine | Begins each record with M, within the requested length. An N-terminal motif already starting with M satisfies this option without an extra M. | On |
Include common motifs | Inserts one complete fixed motif per record. | Off |
Motif type | signal, nuclear, transmembrane, his_tag, or rgd. Visible when motifs are enabled. | signal |
Motif position | start (N-terminal), end (C-terminal), or random. Visible when motifs are enabled. Random placement can reach either end when space permits; a separate start M is preserved. | start |
Amino acid pools
These pools define which residues are sampled, rather than predicting a protein's properties at a particular pH or in a particular structure. Inspect the final amino acid composition when a control needs a measured composition.
| Choice | Random residue pool |
|---|---|
Mixed | A C D E F G H I K L M N P Q R S T V W Y |
Hydrophobic | A V L I M F W P |
Polar | S T N Q Y C |
Charged | D E K R H |
Small | A G S T C |
Aromatic | F Y W |
Fixed motif sequences
| Choice | Inserted sequence |
|---|---|
Signal Peptide | MKLLLLLLLL |
Nuclear Localization | PPKKKRKV |
Transmembrane | LLLLLLLLLLLLLLLLLLLL (20 L residues) |
His-Tag | HHHHHH |
RGD Motif | RGD |
An N-terminal motif begins at the first position unless a separate start M is needed, in which case it follows that M. A C-terminal motif occupies the end of the sequence. These motifs are fixed test patterns; inserting one does not establish secretion, membrane insertion, localization, binding, or expression.
Results
| Result | Contents |
|---|---|
| FASTA text | One record per generated protein, separated by a blank line. |
| Header | Random_Protein_ and its one-based number, followed by length= with the actual amino acid count. The header does not include the composition choice. |
| Download | The same generated text as a .fasta file. |
| Notices | A saved request for the retired charge-balancing setting reports that charge has not been balanced. |
The output contains only the 20 standard amino acid letters, with no stop symbols. It does not generate DNA codons or optimize codon usage. Use protein to DNA when a nucleotide sequence is needed.
When random sequences are useful
Random sequences can test parsers, demonstrate compositional bias, or supply a simple statistical background for a chosen analysis. Uniform sampling does not reproduce natural residue frequencies, evolutionary relationships, or correlations between neighboring residues. Random output also does not establish that a sequence is a suitable biological negative control.
The generator does not balance charge, predict folding, or enforce secondary structure. Net charge depends on ionization and pH; inspect it with a charge plot rather than inferring it from equal counts of residue classes.
Which sequence generator should I use?
| Goal | Tool |
|---|---|
| Sample new amino acid sequences from one of the listed pools | This random protein generator |
| Make nucleotide test sequences with an approximate GC target | Random DNA generator or random RNA generator |
| Sample protein sequences with a learned sequence model | EvoDiff |
| Design sequences for an existing protein backbone | ProteinMPNN |
FAQ
How do I generate proteins of exactly one length?
Set Minimum length (aa) and Maximum length (aa) to the same value. Start methionine and motifs count toward that total.
Why is M present when I select Aromatic or Small?
Include start methionine is enabled by default and fixes the first residue as M. Turn it off to sample only the selected pool, and leave motifs off as well.
Does random protein generation guarantee a functional protein?
No. The generator samples residues and inserts optional sequence patterns. It does not assess biological activity, expression, or foldability.
Related tools
Codon optimization
Optimize coding DNA for a target organism with DNA Chisel while preserving its translation.
DNA mutation generator
Mutate DNA online by exact count or mutation rate, with reproducible controls and FASTA export.
DNAGenIQ (Random DNA sequence generator)
Generate random DNA sequences with controlled length, GC content, and restriction sites.
RNAGenIQ (Random RNA sequence generator)
Generate random RNA test sequences with adjustable GC content and optional RNA-like templates and sequence motifs.
Overlapping peptide generator
Design overlapping peptide libraries with adjustable length, overlap and terminal restrictions. Runs in your browser.
Dimorphite-DL
Generate ligand protonation states over a pH range with Dimorphite-DL.
DNA Shuffle
Shuffle DNA sequences while preserving nucleotide, dinucleotide, or k-mer composition.
Stereoisomer generator
Enumerate stereoisomers from SMILES while preserving assigned stereochemistry by default.
Aliphatic Index
Calculate the aliphatic index of protein sequences to assess thermostability
AlphaFold Database Download
Fetch AlphaFold DB CIF, PDB, BCIF, and PAE JSON files from a UniProt accession.