The EMBOSS program patmatmotifs looks for sequence motifs by searching with a pattern search algorithm through the given protein sequence for the patterns defined in the PROSITE database, compiled by Dr. Amos Bairoch at the University of Geneva. PROSITE is a database of protein families and domains, based on the observation that, while there are a huge number of different proteins, most of them can be grouped, on the basis of similarities in their sequences, into a limited number of families. Proteins or protein domains belonging to a particular family generally share functional attributes and are derived from a common ancestor.