NMR Resolves Phospholamban's Allosteric Regulation of the Sarcoplasmic Reticulum Ca2+-ATPase

Abstract

Disruption of cardiac calcium cycling due to dysregulation of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) by the small transmembrane protein, phospholamban (PLN) leads to severe phenotypes including arrhythmia and dilated cardiomyopathy (DCM). In order to understand how inherited mutations in PLN lead to these severe phenotypes it is essential to map PLN's binding interaction with SERCA and how this binding interaction is modulated by post-translational modifications in PLN.Here we have applied both magic angle spinning (MAS) and oriented solid-state NMR techniques to characterize the structure, dynamics, and topology of monomeric constructs of PLN in complex with SERCA to better understand how post-translational modifications and mutations in PLN alter SERCA's activity. By combining chemical shift perturbations, dipolar couplings, and other structural restraints with molecular dynamics simulations, we have built a model of the PLN-SERCA complex that outlines a mechanism for PLN's allosteric regulation of SERCA via its cytoplasmic domain.