The alpha- and beta-isoforms of the inhibitor protein of the 3',5'-cyclic adenosine monophosphate-dependent protein kinase: characteristics and tissue- and developmental-specific expression.
The inhibitor protein (PKI) of the cAMP-dependent protein kinase was first characterized from rabbit skeletal muscle. More recently a form of PKI was isolated and cloned from rat testis which shares relatively limited amino acid sequence with the rabbit skeletal muscle form. We have now isolated a cDNA from rat brain which encodes a protein corresponding to the rabbit skeletal muscle PKI. This establishes the presence of the "skeletal muscle" and "testis" proteins in the same species and therefore that they clearly represent distinct isoforms. We have also demonstrated that the isoform from testis, like the skeletal muscle isoform, is specific for the cAMP-dependent protein kinase and that it is able to inhibit this enzyme when expressed in cultured JEG-3 cells. Both forms contain the five specific amino acid recognition determinants which have been shown to be required for high affinity binding to the protein kinase catalytic site, although there is some noted lack of conservation of codons used for these residues. Overall, the two rat isoforms are only 41% identical at the amino acid level and 46% at the level of coding nucleotides. We propose that the rabbit skeletal muscle and rat testis forms be designated PKI alpha and PKI beta, respectively. Using Northern blot analysis, we have examined the tissue distribution of the two forms in the rat and their relative expression during development. In the adult rat, mRNA of the PKI alpha species is highest in muscle (both skeletal and cardiac) and brain (cortex and cerebellum).(ABSTRACT TRUNCATED AT 250 WORDS)
Van Patten
S M
SM
Department of Biological Chemistry, School of Medicine, University of California, Davis 95616.
Howard
P
P
Walsh
D A
DA
Maurer
R A
RA
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D001483:Base Sequence; D001923:Brain Chemistry; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D002531:Cerebellum / Q000737:chemistry / Q000254:growth & development; D002822:Choriocarcinoma; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D024510:Muscle Development; D009124:Muscle Proteins / Q000096:biosynthesis; D009132:Muscles / Q000737:chemistry; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D009928:Organ Specificity; D047428:Protein Kinase Inhibitors; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013154:Spleen / Q000737:chemistry / Q000254:growth & development; D013737:Testis / Q000737:chemistry* / Q000254:growth & development; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D047428:Protein Kinase Inhibitors; C015482:protein kinase modulator