Amino acid repeat patterns in protein sequences: Their diversity and structural-functional implications

All the protein sequences from SWISS-PROT database were analyzed for occurr ence of single amino acid repeats, tandem oligo-peptide repeats, and period ically conserved amino acids. Single amino acid repeats of glutamine, serin e, glutamic acid, glycine, and alanine seem to be tolerated to a considerab le extent in many proteins. Tandem oligo-peptide repeats of different types with varying levels of conservation were detected in several proteins and found to be conspicuous, particularly in structural and cell surface protei ns. It appears that repeated sequence patterns may be a mechanism that prov ides regular arrays of spatial and functional groups, useful for structural packing or for one to one interactions with target molecules. To facilitat e further explorations, a database of Tandem Repents in Protein Sequences ( TRIPS) has been developed and is available at URL: http://www.ncl-india.org /trips.