title: Partial structure and hormonal regulation of rabbit liver inhibitor-1; distribution of inhibitor-1 and inhibitor-2 in rabbit and rat tissues.
abstract: Inhibitor-1 purified from rabbit liver could not be distinguished from the skeletal muscle protein by chromatographic, electrophoretic and immunological criteria. Amino acid sequences comprising 68% of rabbit liver inhibitor-1 were identical to the skeletal muscle protein indicating that they are products of a single gene. Total inhibitor-1 activity in heat-treated rabbit liver extracts was similar to that in skeletal muscle extracts, and the phosphorylation state of inhibitor-1 increased from 14% to 42% in rabbit liver in vivo after an intravenous injection of glucagon. Monospecific antibodies to rabbit skeletal muscle inhibitor-1 recognised a single major protein of identical electrophoretic mobility (26 kDa) in each rabbit tissue examined (skeletal muscle, liver, brain, heart, kidney, uterus and adipose). The antibodies also recognised a single major (30 kDa) protein in the same rat tissues, except liver. The results show that while there are interspecies differences in apparent molecular mass, inhibitor-1 is likely to be the same gene product in each mammalian tissue. Inhibitor-1 was not detected in rat liver, either by activity measurements or immunoblotting, irrespective of the age, sex or strain of the animals. Immunoblotting also failed to detect inhibitor-1 in mouse liver, although it was present in guinea pig, porcine and sheep liver. The absence of inhibitor-1 in rat liver indicates that phosphorylation of this protein cannot underlie the increased phosphorylation of hydroxymethylglutaryl-CoA reductase observed after stimulation by glucagon. Monospecific antibodies to rabbit skeletal muscle inhibitor-2 recognised a 31 kDa protein in each rabbit tissue, and a 33 kDa protein in all rat tissues including liver. The results suggest that inhibitor-2 is the same gene product in each mammalian tissue.
authors.affiliation: Department of Biochemistry, University of Dundee, U.K.
authors.forename: L K
authors.initials: LK
authors.lastname: MacDougall
authors.forename: D G
authors.initials: DG
authors.lastname: Campbell
authors.forename: M J
authors.initials: MJ
authors.lastname: Hubbard
authors.forename: P
authors.initials: P
authors.lastname: Cohen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins; D004791:Enzyme Inhibitors / Q000302:isolation & purification*; D005260:Female; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009124:Muscle Proteins / Q000302:isolation & purification*; D009132:Muscles / Q000378:metabolism; D009928:Organ Specificity; D010446:Peptide Fragments / Q000032:analysis; D010766:Phosphorylation; D011506:Proteins / Q000302:isolation & purification* / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D013045:Species Specificity; D000097847:Protein Phosphatase Inhibitory Proteins
chemical_list: D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D010446:Peptide Fragments; D011506:Proteins; C021042:protein phosphatase inhibitor-1; C024833:protein phosphatase inhibitor-2; D000097847:Protein Phosphatase Inhibitory Proteins