Phospholamban is related to the autoinhibitory domain of the plasma membrane Ca(2+)-pumping ATPase.
The Ca2+ pumps of the plasma membrane (PM ATPase) and of sarcoplasmic reticulum (SR ATPase) share a number of structural and functional properties. A major difference is the regulatory mechanism. The PM ATPase contains a C-terminal autoinhibitory domain; calmodulin binds to it, removing the inhibition. The SR ATPase contains a domain that interacts with the inhibitor protein phospholamban when the latter is in the nonphosphorylated state; phosphorylation of phospholamban removes the inhibition. Peptides corresponding to the autoinhibitory domain of the PM ATPase were synthesized and found to inhibit the SR ATPase. A 28-residue peptide (C28W), containing the entire autoinhibitory domain, was the most powerful (IC50 = 15 microM; lmax greater than 90%). The inhibition was Ca2+ dependent and more pronounced at submicromolar Ca2+ concentrations. C28W is about 50% homologous to the cytosolic domain of phospholamban, the hydrophilic portion of which was found to interact directly with calmodulin (Kd = about 700 nM). However, while calmodulin reversed the inhibition of the SR ATPase by C28W, it failed to reverse that induced by nonphosphorylated phospholamban.
Chiesi
M
M
Department of Research, Pharmaceuticals Division, CIBA-GEIGY Limited, Basel, Switzerland.
Vorherr
T
T
Falchetto
R
R
Waelchli
C
C
Carafoli
E
E
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D004285:Dogs; D007700:Kinetics; D008969:Molecular Sequence Data; D009132:Muscles / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D010455:Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D010766:Phosphorylation; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D000099211:Phospholamban
D002118:Calcium; D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D002147:Calmodulin; D010455:Peptides; D000099211:Phospholamban