Molecular cloning of protein phosphatase inhibitor-1 and its expression in rat and rabbit tissues.
A cDNA encoding the complete amino acid sequence of rat protein phosphatase inhibitor-1 was obtained by screening a skeletal muscle library. The coding region represents a 171-residue polypeptide which demonstrated 80% overall identity with the primary sequence of rabbit inhibitor-1. Sequence homology between the rat and rabbit proteins was particularly striking (98% identity) in the NH2-terminal 61 amino acids, which encompass the threonine phosphorylated by cyclic AMP-dependent protein kinase. This domain possesses full inhibitor activity against type-1 protein phosphatases. In contrast, a domain of similar size at the COOH terminus showed only 57% conservation of primary structure between the two proteins. This reflects a remarkable difference in evolutionary pressures experienced by these domains and may emphasize a lesser role for the COOH-terminal region in inhibitor-1 function. Northern hybridization analysis of RNA from rat and rabbit tissues indicated the presence of two mRNAs, a major 0.7-kilobase and a minor 1.8-kilobase mRNA. The highest expression of inhibitor-1 mRNA was noted in skeletal muscle from both species. Analysis of mRNA levels illustrates potential post-transcriptional mechanisms controlling inhibitor-1 expression in some mammalian tissues.
Department of Growth Biochemistry and Physiology, Merck, Sharp and Dohme Research Laboratories, Rahway, New Jersey 07065.
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Elbrecht
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DiRenzo
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RG
Smith
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Shenolikar
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins; D003001:Cloning, Molecular; D004791:Enzyme Inhibitors; D015870:Gene Expression; D015723:Gene Library; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes; D011506:Proteins / Q000235:genetics*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D012689:Sequence Homology, Nucleic Acid
D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D015345:Oligonucleotide Probes; D011506:Proteins; C021042:protein phosphatase inhibitor-1; D012313:RNA