title: Stimulation of the purified erythrocyte Ca2+-ATPase by tryptic fragments of calmodulin.
abstract: Highly purified tryptic peptides of calmodulin have been obtained by high-performance liquid chromatography. Tryptic cleavage of calmodulin in the presence of Ca2+ results in two main fragments which have been identified by analysis of the amino acid composition as 1-77 and 78-148. In the absence of Ca2+, trypsin cleavage yields fragments 1-106, 1-90, and 107-148. Only fragments 78-148 and 1-106 are still able to stimulate the purified Ca2+-ATPase of erythrocytes, albeit much less efficiently on a molar basis, than intact calmodulin. On the other hand, the same fragments were unable to stimulate the calmodulin-dependent cyclic nucleotide phosphodiesterase, even at 1000-fold molar excess (shown also by Newton, D.L., Oldewurtel, M.D., Krinks, M.H., Shiloach, J., and Klee, C.B. (1984) J. Biol. Chem. 259, 4419-4426). This points to the importance of the carboxyl-terminal half of calmodulin and especially of Ca2+-binding region III in the interaction of calmodulin with the Ca2+-ATPase and provides clear evidence that calmodulin interacts differently with different targets. Oxidation of methionine(s) of fragment 78-148 with N-chlorosuccinimide removes the ability of this fragment to stimulate the ATPase.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain; D000252:Calcium-Transporting ATPases / Q000097:blood*; D002147:Calmodulin / Q000494:pharmacology*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification / Q000494:pharmacology*; D014357:Trypsin
chemical_list: D000596:Amino Acids; D002147:Calmodulin; D010446:Peptide Fragments; D014357:Trypsin; D000252:Calcium-Transporting ATPases