title: Evidence that relaxation of hog biliary muscle is mediated by the interaction between the protein inhibitor of cyclic AMP dependent protein kinase and cholecystokinin C-terminal peptides.
abstract: The interaction of various cholecystokinin (CCK) peptides with the protein inhibitor (PK-I) of cyclic AMP dependent protein kinase (A-PK) has been studied. The order of the affinities (ED50) for relaxation of hog biliary muscle by a series of C-terminal peptides of CCK correlated with the order of the potencies for A-PK-catalyzed phosphorylation of the sarcoplasmic reticulum enriched fraction (SR-F) in the muscle. CCK-4 peptide inhibited the PK-I of A-PK. The apparent Km value of the peptide was 11.5 microM. Scatchard plot analysis for the binding of [14C]CCK-6 peptide to the PK-I showed a dissociation constant (Kd) of 11.2 microM. These results indicated that the Kd value agreed with the ED50 value of CCK-6 and the Km value of CCK-4. It is proposed that a receptor for CCK C-terminal peptides is probably a component in the PK-I; binding of the peptides to this site usually results in the relaxation by these allosteric inhibitors of the PK-I.
mesh_terms: D000818:Animals; D001659:Biliary Tract / Q000187:drug effects*; D001665:Binding Sites / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002766:Cholecystokinin / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D013552:Swine
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010446:Peptide Fragments; C015482:protein kinase modulator; D002766:Cholecystokinin; D000242:Cyclic AMP; D011494:Protein Kinases