Cytoplasmic interactions between phospholamban residues 1-20 and the calcium-activated ATPase of the sarcoplasmic reticulum

The Biochemical Journal
P SharmaB A Levine

Abstract

Phospholamban regulates the activity of the calcium-activated ATPase (CaATPase) of cardiac sarcoplasmic reticulum. Equilibrium fluorescence studies have shown that the N-terminal cytoplasmic region of phospholamban (residues 1-20, domain 1) causes a decrease in the intrinsic tryptophan fluorescence of the CaATPase. The interaction of phospholamban residues 1-20 with the CaATPase also results in spectral changes for the extrinsic chromophore FITC covalently attached to the cytoplasmic region of the calcium pump. The fluorescence changes for both reporter groups correlate with a dissociation constant of approximately 40 microM for the complex between phospholamban residues 1-20 and the CaATPase. Complex formation is notably weaker when phospholamban 1-20 is titrated into the CaATPase in the presence of calcium, with altered conformational effects resulting from binding. The interaction of domain 1 of phospholamban with the CaATPase is also reduced upon phosphorylation of phospholamban 1-20 at Ser-16. This region of phospholamban 1-20 is shown by isotope-edited NMR study to be involved in interaction with the CaATPase. Binding of the phosphorylated peptide is not abolished, however, indicating that phospholamban 1-20 remains assoc...Continue Reading

Citations

Jan 24, 2007·Journal of Molecular Biology·Elizabeth VafiadakiAikaterini Kontrogianni-Konstantopoulos
Apr 17, 2008·Pflügers Archiv : European journal of physiology·Elizabeth VafiadakiDespina Sanoudou
Feb 9, 2007·American Journal of Physiology. Cell Physiology·David L StenoienDiana J Bigelow
Jan 25, 2003·Cell Calcium·F WuytackL Missiaen

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