Effect of Ca2+ Binding to 5,5'-Dithiobis(2-nitrobenzoic aoid) Light Chains on Conformational Changes of F-Actin Caused by Myosin Subfragment-1

Abstract

The fluorescent ADP analogue, 1:N6-ethenoadenosine 5'-diphosphate, was incorporated into F-actin in a myosin-free ghost single fibre. Polarized fluorescence measurements of tryptophan residues and 1:N6-ethenoadenosine 5'-diphosphate were performed under a microspectrophotometer to investigate the conformation of F-actin and the changes induced in it by myosin subfragment-1 with 5,5'-dithiobis(2-nitrobenzoic acid) light chains and without them. A relation was found between the conformational state of F-actin and the presence of 5,5'-dithiobis(2-nitrobenzoic acid) light chains. The conformational changes were shown to be controlled by Ca2+ in the presence of 5,5'-dithiobis(2-nitrobenzoic acid) light chains.