Crystal structure of the complex between calyculin A and the catalytic subunit of protein phosphatase 1

The crystal structure of the catalytic subunit of the protein phosphatase 1 (PP1), PP1gamma, in complex with a marine toxin, calyculin A, was determined at 2.0 Angstrom resolution. The metal binding site contains the phosphate group of calyculin A and forms a tight network via the hydrophilic interactions between PP1 and calyculin A. Calyculin A is located in two of the three grooves, namely, in the hydrophobic groove and the acidic groove on the molecular surface. This is the first observation to note that the inhibitor adopts not a pseuclocyclic conformation but an extended conformation in order to form a complex with the protein. The amino acid terminus of calyculin A contributes, in a limited manner, to the binding to PP1gamma, which is consistent with findings from the studies of dose-inhibition analysis.