Question

In some cases when a single peptide is used to search against a database, such as expasy.org, several proteins are found to correspond to the sequence. Why is this? Thoroughly explain.

Answer 1

Sequence searches are performed based on pattern matching of the array of sequence of interest.If a single peptide is searched across the protein repository like expasy.org.,the resulting sequences may be peptides,entire protein sequences or repeats of the protein sequence that is queried.The amino acid sequence of the peptide may be a motif in different proteins or a functional unit,hence the peptide may have matches of several proteins corresponding to the sequence.

This may have insights on unknown functions or sometimes may give a completely irrelevant data not related to query.

Some proteins that are retrieved may have single amino acid substituitions on the peptide sequence.