Protein subfamily

Protein subfamily is a level of protein classification, based on their close evolutionary relationship. It is below the larger levels of protein superfamily and protein family.[1]

Proteins typically share greater sequence and function similarities with other subfamily members than they do with members of their wider family.[1][2] For example, in the Structural Classification of Proteins database classification system, members of a subfamily share the same interaction interfaces and interaction partners.[3] These are stricter criteria than for a family, where members have similar structures, but may be more distantly related and so have different interfaces. Subfamilies are assigned by a variety of methods, including sequence similarity,[4] motifs linked to function,[5] or phylogenetic clade.[6][7] There is no exact and consistent distinction between a subfamily and a family. The same group of proteins may sometimes be described as a family or a subfamily, depending on the context.