Biology subjects

Fernandez-de Gortari, E.

Publications and source records attributed to Fernandez-de Gortari, E..

2 recordsLinked to original sources

bioRxiv2020

Conserved luminal C-terminal domain dynamically controls interdomain communication in sarcolipin

ABSTRACTSarcolipin (SLN) mediates Ca2+ transport and metabolism in muscle by regulating the activity of the Ca2+ pump SERCA. SLN has a conserved luminal C-terminal domain that contributes to the its functional divergence among homologous SERCA regulators, but the precise mechanistic role of this domain remains poorly understood. We used all-atom molecular dynamics (MD) simulations of SLN totaling 77.5 μs to show that the N- (NT) and C-terminal (CT) domains function in concert. Analysis of the MD simulations showed that serial deletions of SLN C-terminus does not affect the stability of the peptide nor induce dissociation of SLN from the membrane but promotes a gradual decrease in both tilt angle of the transmembrane helix and the local thickness of the lipid bilayer. Mutual information analysis showed that the NT and CT domains communicate with each other in SLN, and that interdomain communication is partially or completely abolished upon deletion of the conserved segment Tyr29-Tyr31 as well as by serial deletions beyond this domain. Phosphorylation of SLN at residue Thr5 also induces changes in the communication between the CT and NT domains, thus providing additional evidence for interdomain communication within SLN. We found that interdomain communication is independent of the force field used and lipid composition, thus demonstrating that communication between the NT and CT domains is an intrinsic functional feature of SLN. We propose the novel hypothesis that the conserved C-terminus is an essential element required for dynamic control of SLN regulatory function.Competing Interest StatementThe authors have declared no competing interest.View Full Text

biophysics↗

bioRxiv2018

Structural basis for relief of the sarcoplasmic reticulum Ca2+-ATPase inhibition by phospholamban at saturating Ca2+ conditions

We have performed extensive atomistic molecular dynamics simulations to probe the structural mechanism for relief of sarcoplasmic reticulum Ca2+-ATPase (SERCA) inhibition by phospholamban (PLB) at saturating Ca2+ conditions. Reversal of SERCA-PLB inhibition by saturating Ca2+ operates as a physiological rheostat to reactivate SERCA function in the absence of PLB phosphorylation. Simulation of the inhibitory complex at super-physiological Ca2+ concentrations ([Ca2+]=10 mM) revealed that calcium ions interact primarily with SERCA and the lipid headgroups, but not with the cytosolic domain of PLB or the cytosolic side of the SERCA-PLB interface. At this [Ca2+], a single Ca2+ ion is translocated from the cytosol to the transmembrane transport sites. We used this Ca2+-bound complex as an initial structure to simulate the effects of saturating Ca2+ at physiological conditions ([Ca2+]total{approx}400 M). At these conditions, ~30% of the Ca2+-bound complexes exhibit structural features that correspond to an inhibited state. However, in ~70% of the Ca2+-bound complexes, Ca2+ moves to transport site I, recruits Glu771 and Asp800, and disrupts key inhibitory contacts involving conserved PLB residue Asn34. Structural analysis showed that Ca2+ induces only local changes in interresidue inhibitory interactions, but does not induce dissociation, repositioning or changes in the structural dynamics of PLB. Upon relief of SERCA inhibition, Ca2+ binding produces a productive site I configuration that is sufficient for subsequent SERCA activation. We propose that at saturating [Ca2+] and in the absence of PLB phosphorylation, binding of a single Ca2+ ion in the transport sites rapidly shifts the equilibrium toward a non-inhibited SERCA-PLB complex.

biophysics↗