Effect of Ca2+ on conformation of actin in the F-actin--heavy meromyosin complex.

: The polarized fluorescence of intrinsic tryptophan residues and the birefringence of ghost muscle fibres of rabbit were measured during thin filaments binding to heavy meromyosin containing 5,5'-dithiobis [2-nitrobenzoic acid] light chains and to those devoid of them with a view of investigating conformational changes in F-actin. Ca2+ binding to heavy meromyosin containing 5,5'-dithiobis [2-nitrobenzoic acid] light chains was shown to affect the character of these changes during the formation of the F-actin - heavy meromyosin complex.