Mobile segments in rabbit skeletal muscle F‐actin detected by 1H nuclear magnetic resonance spectroscopy

FEBS Letters

Kalbitzer, Hans Robert¹  Heintz, Daniela¹  Ślósarek, Genowefa¹ 

[1] Max-Planck-Institute for Medical Research, Dept. Biophysics, Jahnstr.29, D-69120 Heidelberg, Germany

关键词: Actin;    Mobility;    1H NMR;    Muscle;    G-actin;    globular actin;    F-actin;    filamentous actin;   

DOI  :  10.1016/0014-5793(94)00894-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Polymerization of actin by increasing the ionic strength leads to a quenching of almost all ¹H NMR signals. Surprisingly, distinct signals with relatively small line widths can still be observed in actin filaments (F-actin) indicating the existence of mobile, NMR visible residues in the macromolecular structure. The intensity of the F-actin spectrum is much reduced if one replaces Mg²⁺ with Ca²⁺, and a moderate reduction of the signal intensity can also be obtained by increasing the ionic strength. These results can be explained in a two-state model of the actin protomers with a M- (mobile) state and a I- (immobile) state in equilibrium. In the M-state a number of residues in the actin protomer are mobile and give rise to observable NMR signals. This equilibrium is shifted towards the I-state specifically by replacing Mg²⁺ with Ca²⁺-ions and unspecifically by addition of monovalent ions such as K₊. The binding of phalloidin to its high-affinity site in the filaments does not influence the equilibrium between M- and I-state. Phalloidin itself is completely immobilized in F-actin, its exchange with the solvent being slow on the NMR time scale.

【 授权许可】

Unknown