Conformational dynamics of recoverin's Ca2+-myristoyl switch probed by 15N NMR relaxation dispersion and chemical shift analysis.

ABSTRACT: Recoverin, a member of the neuronal calcium sensor (NCS) branch of the calmodulin superfamily, serves as a calcium sensor in retinal rod cells. Ca(2+) -induced conformational changes in recoverin promote extrusion of its covalently attached myristate, known as the Ca(2+)-myristoyl switch. Here, we present nuclear magnetic resonance (NMR) relaxation dispersion and chemical shift analysis on (15) N-labeled recoverin to probe main chain conformational dynamics. (15) N NMR relaxation data suggest that Ca(2+)-free recoverin undergoes millisecond conformational dynamics at particular amide sites throughout the protein. The addition of trace Ca(2+) levels (0.05 equivalents) increases the number of residues that show detectable relaxation dispersion. The Ca(2+)-dependent chemical shifts and relaxation dispersion suggest that recoverin has an intermediate conformational state (I) between the sequestered apo state (T) and Ca(2+) saturated extruded state (R): T ? I ? R. The first step is a fast conformational equilibrium ([T]/[I] < 100) on the millisecond time scale (?(ex) ?? < 1). The final step (I ? R) is much slower (?(ex) ?? > 1). The main chain structure of I is similar in part to the structure of half-saturated E85Q recoverin with a sequestered myristoyl group. We propose that millisecond dynamics during T ? I may transiently increase the exposure of Ca(2+)-binding sites to initiate Ca(2+) binding that drives extrusion of the myristoyl group during I ? R.

SUBMITTER: Xu X 

PROVIDER: S-EPMC3092842 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature