The effect of N-terminal acetylation on Ca(2+)-ATPase inhibition by phospholamban.
The peptide Ac-MEKVQYLTRSAIRRASTIEMPQQAR (Ac-PLB(1-25)) representing residues 1-25 of phospholamban (PLB) inhibited the maximal activity of the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum by about 53%, with a Kd value of 5 microM; the equivalent non-acetylated peptide PLB(1-25) had no effect. However, it was found that the non-acetylated peptide increased the effective Kd value for inhibition by Ac-PLB(1-25) consistent with competitive binding to the ATPase, with a Kd value of 8 microM for PLB(1-25). The non-acetylated peptide must therefore be able to bind to the ATPase, but in a conformation that does not lead to inhibition of the ATPase. The identity of the N-terminal residue is important in determining the strength of binding; replacement of the Met residue by Ile led to fourfold weaker binding, again with only binding of the acetylated peptide leading to inhibition of ATPase activity.
Starling
A P
AP
Department of Biochemistry, University of Southampton, United Kingdom.
Sharma
R P
RP
East
J M
JM
Lee
A G
AG
D000107:Acetylation; D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D000099211:Phospholamban
D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D010446:Peptide Fragments; D000099211:Phospholamban