title: Inhibitors of protein phosphatase-1. Inhibitor-1 of bovine adipose tissue and a dopamine- and cAMP-regulated phosphoprotein of bovine brain are identical.
abstract: Protein phosphatase inhibitor-1 was purified from bovine adipose tissue. The protein had an apparent molecular mass of 32 kDa by SDS/PAGE and a Stokes' radius of 3.4 nm. It was phosphorylated by cAMP-dependent protein kinase on a threonyl residue; this phosphorylation was necessary for inhibition of protein phosphatase-1. Bovine adipose tissue inhibitor-1 was compared directly with rabbit skeletal muscle inhibitor-1 and with a 32000-Mr, dopamine- and cAMP-regulated phosphoprotein from bovine brain (DARPP-32), also an inhibitor of protein phosphatase-1. By the following biochemical and immunochemical criteria, bovine adipose tissue inhibitor-1 was found to be very similar and possibly identical to DARPP-32 and was clearly distinct from skeletal muscle inhibitor-1: molecular mass by SDS/PAGE; Stokes' radii; phosphorylation on threonine residues; Staphylococcus-aureus-V8-protease-generated peptide patterns analyzed by SDS/PAGE; tryptic phosphopeptide maps analysed by two-dimensional thin-layer electrophoresis/chromatography; elution on reverse-phase HPLC; chymotryptic peptide maps as analysed by reverse-phase HPLC; amino acid composition; antibody recognition by immunoprecipitation and immunoblotting; effect of cyanogen bromide cleavage on protein phosphatase inhibitor activity. Based on these results we conclude that bovine brain and adipose tissue contain an identical phosphoprotein inhibitor of protein phosphatase-1 (DARPP-32), which is distinct from that of skeletal muscle (inhibitor-1).
authors.affiliation: Department of Physiological Chemistry, University of Lund, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Strålfors
authors.forename: H C
authors.initials: HC
authors.lastname: Hemmings
authors.forename: P
authors.initials: P
authors.lastname: Greengard
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003429:Cross Reactions; D003488:Cyanogen Bromide; D000242:Cyclic AMP / Q000494:pharmacology*; D004298:Dopamine / Q000494:pharmacology*; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D004586:Electrophoresis / Q000379:methods; D004791:Enzyme Inhibitors / Q000302:isolation & purification* / Q000494:pharmacology; D009132:Muscles / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000302:isolation & purification*; D010449:Peptide Mapping; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010750:Phosphoproteins / Q000302:isolation & purification*; D010766:Phosphorylation; D011233:Precipitin Tests; D054645:Protein Phosphatase 1; D011817:Rabbits
chemical_list: D000596:Amino Acids; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; D004791:Enzyme Inhibitors; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D000242:Cyclic AMP; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D003488:Cyanogen Bromide; D004298:Dopamine