Identification, purification, and characterization of a novel serine/threonine protein phosphatase from bovine brain.
A novel serine/threonine protein phosphatase is identified, and the catalytic subunit, obtained from a detergent extraction of the pellet generated by a 100,000 x g centrifugation of a whole bovine brain homogenate, is purified and characterized. The protein phosphatase, designated as PP3, has a Mr of 36,000, does not require divalent cations for activity, is stimulated rather than inhibited by inhibitor 2, is inhibited by both okadaic acid and microcystin-LR with an intermediate IC50 compared to type 1 and type 2A protein phosphatases, and preferentially dephosphorylates the beta subunit of phosphorylase kinase. Substrate specificity, immunoblotting with type-specific antisera, and the amino acid sequences of peptides derived from PP3 indicate that PP3 is not an isoform of any known serine/threonine protein phosphatase.
Honkanen
R E
RE
Molecular Oncology Program, Cancer Research Center of Hawaii, University of Hawaii, Honolulu 96813.
Zwiller
J
J
Daily
S L
SL
Khatra
B S
BS
Dukelow
M
M
Boynton
A L
AL
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002384:Catalysis; D002417:Cattle; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006493:Heparin / Q000494:pharmacology; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000302:isolation & purification*; D010766:Phosphorylation; D011479:Protamines / Q000494:pharmacology; D012694:Serine / Q000737:chemistry*; D013912:Threonine / Q000737:chemistry*
D011479:Protamines; D013912:Threonine; D012694:Serine; D006493:Heparin; D010749:Phosphoprotein Phosphatases