Influence of the bound nucleotide on the molecular dynamics of actin

Abstract

Rotational dynamics of actin spin‐labelled with maleimide probes at the reactive thiol Cys‐374 were studied. Replacement of the bound nucleotide by Br8ATP in G‐actin and Br8ADP in F‐actin causes significant increase of the rotational correlation time of the spin probe, indicating reduced motion in both G and F‐actin. The orientation dependence of the electron paramagnetic resonance spectra in oriented F‐actin filaments revealed an altered molecular order of the probe when the nucleotide was a Br‐substituted one. The bound nucleotide affects the myosin S1 ATPase activation by actin; both Vmax, and Kactin decreased significantly when the bound nucleotide of actin was Br8ADP. Copyright © 1988, Wiley Blackwell. All rights reserved