Background

Protein phosphatase 1 is a ubiquitous eukaryotic protein serine/threonine phosphatase involved in the regulation of various cell functions. Substrate specificity is determined by the binding of a regulatory subunit to the PP1 catalytic subunit. It is estimated that over fifty different regulatory subunits exist.The myosin phosphatase holoenzyme is composed of three subunits: PP1c, a targeting/regulatory subunit, and a 20 kDa subunit of unknown function. MYPT binding to PP1cδ alters the conformation of the catalytic cleft and increases enzyme activity and specificity. Two MYPT isoforms that are 61% identical have been described. MYPT1 is widely expressed, while MYPT2 expression appears to be exclusive to heart and brain. Related family members include MBS85, MYPT3, and TIMAP.Myosin phosphatase regulates the interaction of actin and myosin in response to signaling through the small GTPase Rho. Rho activity inhibits myosin phosphatase via Rho-associated kinase. Phosphorylation of MYPT1 at Thr696 and Thr853 results in phosphatase inhibition and cytoskeletal reorganization.

References

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