title: Subunit structure and regulation of protein phosphatase-1 in rat liver nuclei.
abstract: The activity of protein phosphatase-1 in rat liver nuclei (PP-1N) was decreased by up to 97% by associated inhibitory polypeptides, depending on the assay and extraction conditions. These inhibitors were rapidly degraded by endogenous proteases, resulting in the accumulation of active heat-stable intermediates. Two major species of PP-1N could be differentiated by fractionation of a nuclear extract. PP-1NR111 contained, besides the delta-isoform of the catalytic subunit, an inhibitory polypeptide of 111 kDa. PP-1NR41 was found to be an inactive heterodimer between the delta-isoform of the catalytic subunit and NIPP-1, a nuclear inhibitor of PP-1, which in its undegraded form is heat labile and migrates during SDS-polyacrylamide gel electrophoresis as a polypeptide of 41 kDa. Native hepatic NIPP-1 displayed a reduced affinity for the catalytic subunit after phosphorylation by protein kinase A in vitro and after glucagon-induced phosphorylation in vivo.
authors.affiliation: Afedling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Belgium.
authors.forename: I
authors.initials: I
authors.lastname: Jagiello
authors.forename: M
authors.initials: M
authors.lastname: Beullens
authors.forename: W
authors.initials: W
authors.lastname: Stalmans
authors.forename: M
authors.initials: M
authors.lastname: Bollen
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D005260:Female; D008099:Liver / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology
chemical_list: D014107:Tosyllysine Chloromethyl Ketone; D014108:Tosylphenylalanyl Chloromethyl Ketone; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1