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Impact of methionine oxidation on calmodulin structural dynamics.

Abstract：

:We have used electron paramagnetic resonance (EPR) to examine the structural impact of oxidizing specific methionine (M) side chains in calmodulin (CaM). It has been shown that oxidation of either M109 or M124 in CaM diminishes CaM regulation of the muscle calcium release channel, the ryanodine receptor (RyR), and that mutation of M to Q (glutamine) in either case produces functional effects identical to those of oxidation. Here we have used site-directed spin labeling and double electron-electron resonance (DEER), a pulsed EPR technique that measures distances between spin labels, to characterize the structural changes resulting from these mutations. Spin labels were attached to a pair of introduced cysteine residues, one in the C-lobe (T117C) and one in the N-lobe (T34C) of CaM, and DEER was used to determine the distribution of interspin distances. Ca binding induced a large increase in the mean distance, in concert with previous X-ray crystallography and NMR data, showing a closed structure in the absence of Ca and an open structure in the presence of Ca. DEER revealed additional information about CaM's structural heterogeneity in solution: in both the presence and absence of Ca, CaM populates both structural states, one with probes separated by ∼4nm (closed) and another at ∼6nm (open). Ca shifts the structural equilibrium constant toward the open state by a factor of 13. DEER reveals the distribution of interprobe distances, showing that each of these states is itself partially disordered, with the width of each population ranging from 1 to 3nm. Both mutations (M109Q and M124Q) decrease the effect of Ca on the structure of CaM, primarily by decreasing the closed-to-open equilibrium constant in the presence of Ca. We propose that Met oxidation alters CaM's functional interaction with its target proteins by perturbing this Ca-dependent structural shift.

journal_name

Biochem Biophys Res Commun

journal_title

Biochemical and biophysical research communications

authors

McCarthy MR,Thompson AR,Nitu F,Moen RJ,Olenek MJ,Klein JC,Thomas DD

doi

10.1016/j.bbrc.2014.11.091

subject

Has Abstract

pub_date

2015-01-09 00:00:00

pages

567-72

issue

eissn

0006-291X

issn

1090-2104

pii

S0006-291X(14)02123-8

journal_volume

456

pub_type

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Impact of methionine oxidation on calmodulin structural dynamics.