Domain

Domains are regions of contiguous polypeptide chain that have been described as compact, local, and semi-independent units. Within a protein, domains can be anything from independant globular units joined only by a flexible length of polypeptide chain, to units which have a very extensive interface. There are a number of algorithms that have been developed to detect domains automatically, some of which have been incorporated into the CATH update protocol. Many domains, however, still have to be determined manually before being classified.