Quantitative relationship between the protein secondary structure in cardiac sarcolemma and the activity of the membrane-bound Ca2+-ATPase.
In the absence of ATP, increasing concentrations of calcium within a range between 0.1--8.0 mmol . 1(-1) gradually lowered the alpha-helix content of proteins in rat heart sarcolemma requiring no energy supply. In the presence of ATP, similar concentrations of calcium stepwise activated the sarcolemmal low-affinity Ca2+-ATPase. A mathematical analysis of the data obtained revealed a quantitative relationship between calcium-induced stimulation of the Ca2+-ATPase activity and a diminution of the alpha-helix contents of membrane proteins in cardiac sarcolemma. The cooperation between changes in protein conformation and energy consumption in relation to the supposed role of low-affinity Ca2+-ATPase in gating the calcium channel are discussed.
Vrbjar
N
N
Ziegelhöffer
A
A
Breier
A
A
Soós
J
J
Dzurba
A
A
Monosíková
R
R
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D004789:Enzyme Activation; D007425:Intracellular Membranes / Q000201:enzymology*; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology* / Q000378:metabolism*; D011487:Protein Conformation; D051381:Rats; D012508:Sarcolemma / Q000201:enzymology*
D008565:Membrane Proteins; D000252:Calcium-Transporting ATPases; D002118:Calcium