ZMPP2, a novel type-2C protein phosphatase from maize

A cDNA clone was selected as a candidate for the catalytic subunit of phosp ho-pyruvate dehydrogenase phosphatase (PDP) by screening a Zea mays express ed sequence tag database with the bovine PDP deduced amino acid sequence. B oth strands of the cDNA were completely sequenced. The maize clone contains an open reading frame of 1098 base pairs that encodes a polypeptide of 401 27 Da, ZMPP2. The deduced amino acid sequence of ZMPP2 contains the five PP 2C signature domains, as does PDP. However, the expression pattern of ZMPP2 , determined by reverse transcriptase-polymerase chain reaction, was differ ent from those of the maize pyruvate dehydrogenase Ela subunit and pyruvate dehydrogenase kinase. Additionally, the predicted subcellular location of ZMPP2 is cytoplasmic, while the pyruvate dehydrogenase complex, regulated b y reversible phosphorylation, is mitochondrial. Thus, ZMPP2 is a PP2C-type protein phosphatase related to but distinct from PDP.