PROSITE: a dictionary of sites and patterns in proteins. Nucleic Acids Res

PROSITE is a compilation of sites and patterns found in protein sequences; it can be used as a method of determining the function of uncharacterized proteins translated from genomic or cDNA sequences. In some cases the sequence of an unknown protein is too distantly related to any protein of known structure to detect its resemblance by overall sequence alignment, but relationships can be revealed by the occurrence in its sequence of a particular cluster of residue types which is variously known as a pattern, motif, signature, or fingerprint. These motifs arise because specific region(s) of a protein which may be important, for example, for their binding properties or for their enzymatic activity are conserved in both structure and sequence. These structural requirements impose very tight constraints on the evolution of these small but important portion(s) of a protein sequence. The use of protein sequence patterns to determine th