The hydrophilic domain of phospholamban inhibits the Ca2+ transport step of the Ca(2+)-ATPase.
The peptide MEKVQYLTRSAIRRASTIEMPQQAR-Cys corresponding to residues 1-25 of phospholamban was found to inhibit the ATPase activity of skeletal muscle Ca(2+)-ATPase, but to have no effect on the Ca(2+)-dependence of its activity. The peptide was found to decrease the rate of the Ca2+ transport step (E1PCa2-->E2P) by a factor of 2.4. The rate of this same step was decreased by poly(L-Arg) by a factor of 2.2. The peptide shifted the E2-E1 equilibrium of the ATPase towards E1 by a factor of 4 due to stronger binding to the E1 than to the E2 conformation of the ATPase; dissociation constants for binding to E1 and E2 were estimated as 3 and 10 microM respectively. The peptide had no effect on the level of phosphorylation by Pi in the absence of Ca2+ or on the rate of phosphorylation by ATP in the presence of Ca2+.
Department of Biochemistry, University of Southampton, U.K.
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G
Hughes
J M
JM
East
A G
AG
Lee
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002851:Chromatography, High Pressure Liquid; D003198:Computer Simulation; D008954:Models, Biological; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D013050:Spectrometry, Fluorescence; D000099211:Phospholamban
D000251:Adenosine Triphosphatases; D002118:Calcium; D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D000099211:Phospholamban