title: Gramicidin S inhibition of the Ca2+-ATPase of human red blood cells.
abstract: The cationic amphiphilic polypeptide gramicidin S inhibits the Ca2+-ATPase of human red-cell membranes by lowering the maximum velocity of the high-affinity component and the apparent affinity of the low-affinity component of the velocity-versus-ATP concentration curve of the enzyme. Gramicidin S does not alter the apparent affinity of the Ca2+-ATPase for Ca2+. Calmodulin is not essential for the inhibition, but increases the sensitivity of the enzyme to the inhibitor. The effects of gramicidin S on the Ca2+-ATPase can be reversed with phosphatidylcholine vesicles but not with buffer solutions, suggesting that gramicidin S acts from the lipid phase of the membrane.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002147:Calmodulin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000201:enzymology*; D006096:Gramicidin / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics
chemical_list: D002147:Calmodulin; D006096:Gramicidin; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium