Identification, purification, and characterization of a novel serine/threonine protein phosphatase from bovine brain. |
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Authors: | R E Honkanen J Zwiller S L Daily B S Khatra M Dukelow A L Boynton |
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Affiliation: | Molecular Oncology Program, Cancer Research Center of Hawaii, University of Hawaii, Honolulu 96813. |
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Abstract: | 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. |
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