Site-Specific Methionine Oxidation and Calmodulin Molecular Dynamics

Abstract

We have examined the structural consequences of methionine (Met) oxidation in the calcium signaling protein calmodulin (CaM) using molecular dynamics simulations. Protein oxidation by reactive oxygen species (ROS) is a critical element of cell function, but in the context of oxidative stress, has been implicated in disease progression and biological aging. Calmodulin function is intimately tied to muscle redox state through methionine oxidation by ROS and reduction by methionine sulfoxide reductases. Our goal is to bridge our understanding of muscle dysfunction and protein oxidation with atomic-level insights into site-specific methionine oxidation and calmodulin structural dynamics. We have carried out multiple 100 ns molecular dynamics simulations of explicitly solvated calmodulin starting from the calcium bound (1cll) and apo (1cfc) crystal structures. Results from preliminary simulations suggest that calcium bound CaM is structurally insensitive to methionine oxidation, while methionine oxidation in apo CaM causes considerable changes in the distribution of conformational states. Our work is a component of a larger study in which spectroscopic distance measurements and nuclear magnetic resonance experiments are being carried out for site-specifically oxidized CaM in both the calcium bound and apo biochemical states. We expect that our in silico results will bring atomic-level insight to spectroscopic measurements, and will be integral to creating a more complete model for oxidation-induced changes in calmodulin structural dynamics. Further, we anticipate that our results will be applicable to the many biological and pharmaceutical contexts in which a detailed understanding of protein oxidation, function and structure relationships is sought. This work is supported by NIH (2R37AG026160-06) and the Minnesota Supercomputing Institute.