Sarcolipin Promotes Uncoupling of the SERCA Ca²⁺ Pump by Inducing a Structural Rearrangement in the Energy-Transduction Domain

We have performed microsecond (μs) molecular dynamics simulation (MDS) to identify structural mechanisms for sarcolipin (SLN) uncoupling of Ca²⁺ transport from ATP hydrolysis for the sarcoplasmic reticulum Ca²⁺-ATPase (SERCA). SLN regulates muscle metabolism and energy expenditure to provide resistance against diet-induced obesity and extreme cold. MDS demonstrated that the cytosolic domain of SLN induces a salt bridge-mediated structural rearrangement in the energy-transduction domain of SERCA. We propose that this structural change uncouples SERCA by perturbing Ca²⁺ occlusion at residue E309 in transport site II, thus facilitating Ca²⁺ backflux to the cytosol. Our results have important implications for designing muscle-based therapies for human obesity.