The influence of divalent cations on the dynamic properties of actin filaments: A spectroscopic study

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Abstract

The principal aim of this investigation was to study the change of the protein flexibility and/or conformational properties of actin filaments upon the replacement of Ca2+ by Mg2+. The temperature dependence of the fluorescence lifetime and the anisotropy decay of N-(iodoacetyl)-N'-(5- sulfo-1-naphthyl)ethylenediamine (IAEDANS) attached covalently to the Cys374 residue of actin were measured. Saturation transfer electron paramagnetic resonance (ST-EPR) experiments were also carried out using N- (1-oxyl-2,2,6,6-tetramethyl-4-piperidinyl)-maleimide (MSL) attached to the same residue (Cys374). The Arrhenius analysis of the temperature dependence of the fluorescence lifetimes shows that for Mg-F-actin, both the activation energy (E*) and the frequency factor (A) are smaller than they are for Ca-F-actin. The longer rotational correlation times resolved in the fluorescence experiments are larger in the Mg2+-loaded form of the actin filament between 6°C and 28°C, but this difference becomes negligible above 28°C. The results of saturation transfer electron paramagnetic resonance measurements on maleimide spin-labeled actin filaments indicate that the replacement of Ca2+ by Mg2+ induced a decrease of the mobility of the label on the sub-millisecond time scale. Based upon these results, we concluded that the filaments polymerized from Ca-actin are more flexible than the filaments of Mg-actin.

Original languageEnglish
Pages (from-to)3015-3022
Number of pages8
JournalBiophysical journal
Volume75
Issue number6
DOIs
Publication statusPublished - Dec 1998

ASJC Scopus subject areas

  • Biophysics

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