Conformational dynamics of recoverin's Ca(2+) -myristoyl switch probed by (15) N NMR relaxation dispersion and chemical shift analysis.

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Conformational dynamics of recoverin's Ca(2+) -myristoyl switch probed by (15) N NMR relaxation dispersion and chemical shift analysis.

Conformational dynamics of recoverin's Ca(2+) -myristoyl switch probed by (15) N NMR relaxation dispersion and chemical shift analysis.

Proteins. 2011 Feb 16;

Authors: Xu X, Ishima R, Ames JB

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. Proteins 2011; © 2011 Wiley-Liss, Inc.

PMID: 21465563 [PubMed - as supplied by publisher]



Source: PubMed