Phospholamban modulates the functional coupling between nucleotide domains in Ca-ATPase oligomeric complexes in cardiac sarcoplasmic reticulum.

ABSTRACT: Oligomeric interactions between Ca-ATPase polypeptide chains and their modulation by phospholamban (PLB) were measured in native cardiac sarcoplasmic reticulum (SR) microsomes. Progressive modification of Lys(514) with fluorescein 5-isothiocyanate (FITC), which physically blocks access to the nucleotide binding site by ATP, demonstrates that Ca-ATPase active sites function independently of one another prior to the phosphorylation of PLB. However, upon cAMP-dependent protein kinase (PKA) phosphorylation of PLB, a second-order dependence between residual enzyme activity and the fraction of active sites is observed, consistent with a dimeric functional complex. Complementary distance measurements were made using FITC or 5-iodoacetamidofluorescein (IAF) bound to Cys(674) within the N- or P-dom

SUBMITTER: Chen LT 

PROVIDER: S-EPMC2765579 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature