Protein phosphatase 1, regulatory (inhibitor) subunit 1A Adenovirus

The phosphorylation and dephosphorylation of proteins on serine and threonine residues is an essential means of regulating a broad range of cellular functions in eukaryotes, including division, homeostasis and apoptosis. A group of proteins that are intimately involved in this process are the serine/threonine protein phosphatases. The protein phosphatase (PP) holoenzyme is a trimeric complex composed of a regulatory subunit, a variable subunit and a catalytic subunit. Four major families of protein phosphatase catalytic subunits have been identified and are designated PP1, PP2A, PP2B (calcineurin) and PP2C. An additional protein phosphatase catalytic subunit, PPX or PP4, is a member of a potentially novel PP family. The PP1 family comprises subfamily members PP1(alpha), PP1(beta) and PP1(gamma). The PP2A family comprises subfamily members PP2A(alpha) and PP2A(beta). The PP2B family comprises subfamily members PP2B-A(alpha), PP2B-A(beta) and PP2B-A(gamma). The PP2C family comprises PP2C(alpha), PP2C(beta) and PP2C(gamma). Wip1, a protein identified in the p53 DNA response pathway, has also been identified as a potential member of the PP2C family. Regulatory subunits include nuclear inhibitor of PP1 (NIPP1), PP2A-A(alpha) and -A(beta), PP2A-B(alpha), -B(beta) and -B(gamma), PP2A-C(alpha) and -C(beta), PP2A-B56-(alpha) and -B56-(beta), PR48 and PP2B-B1 and -B2.