[Effect of hypothyreosis on actin subdomain-1 movement induced by myosin subfragment 1-binding in fast and slow rat skeletal muscles].

PMID 19799356


Orientation and mobility of fluorescent probe N-((iodoacetyl)-(1-naphtyl-5-sulpho-ethylenediamine)(1.5-IAEDANS)) specifically bound to Cys-374 of actin in ghost muscle fibers isolated from fast and slow rat muscles were studied by polarized fluorimetry in the absence and presence of myosin subfragment-1 (S1) in intact rats and in the animals with gradual (during 2-5 weeks) reduction of thyroid hormones synthesis (hypothyreosis development). S1 binding to F-actin of ghost muscle fibers was shown to induce changes in orientation of the dipoles of the fluorescent probe 1.5-IAEDANS and in the relative amount of the randomly oriented fluorophores that indicated changes in actin subdomain-1 orientation and mobility resulting from the formation of its strong binding with S1. This effect is markedly inhibited by hypothyreosis development. The maximal effect of hypothyreosis is observed after 34 days of disease development. It is suggested that the change of thyroid status in the muscle inhibits the ability of F-actin to form strong binding with myosin which is essential for force generation.