Ion mobility spectrometry and molecular dynamics simulations of gas-phase apocalmodulin.

摘要

Calmodulin is a calcium-binding protein that plays a critical role in cellular activity. The calcium-free (apocalmodulin) form has a unique dumbbell-shaped structure with two globular domains that are separated by a solvent-exposed central helix. In this study we analyze the conformation of apocalmodulin ions in vacuo using both experimental and computational techniques. Experiments were performed using ion mobility spectrometry (IMS) and computations were based on molecular dynamics (MD) simulations. This is the first study that combines IMS with MD simulations to investigate the unfolding behaviour of anhydrous apocalmodulin. Three apocalmodulin conformational families are identified over the +7 to +17 charge states. Our experimental cross sections agree well with those reported in the literature and there is good qualitative and quantitative agreement between our IMS and MD data. We speculate that the unfolding dynamics of apocalmodulin in solution are conserved in vacuo and are thus intrinsic to the protein.