Study of Tropomyosin Labelled with a Fluorescent Probe by Pulse Fluorimetry in Polarized Light

Abstract

Tropomyosin has been labelled with a fluorescent probe N-iodoacetyl-N′-(5-sulfo-1-naphthyl)-ethylenediamine which is presumed to bind preferentially to the unique reactive cysteine residue of the α chain. Anisotropy decay measurements show that tropomyosin monomer and polymer are flexible molecules. This flexibility decreases when troponin interacts with tropomyosin, and is partially restored by a micromolar concentration of Ca²⁺.