THE INFLUENCE OF CALDESMON ON STRONG BINDING OF MYOSIN WITH ACTIN IN DENERVATED RAT SKELETAL MUSCLES
V. P. Kirillina,1 A. Jakubiec-Puka,2 Yu. S. Borovikov 1
1 Institute of Cytology RAS, St. Petersburg, Russia, and
2 Nencki Institute of Experimental Biology PAN, Warszawa, Poland;
e-mail: boroviko@mail.cytspb.rssi.ru
The effect of caldesmon (CaD) on conformational changes in F-actin modified by fluorescent probe TRITC-phalloidin
was investigated by polarized fluorimetry. Changes were induced by a subfragment-1 (S-1) of myosin in the absence or
presence of CaD in ghost muscle fibers obtained from intact and denervated slow (SOL) and fast (EDL) skeletal muscles
of rats. S-1 binding to actin of both SOL and EDL muscles was shown to cause changes in polarized parameters of
TRITC-phalloidin typical for a strong actin-myosin binding as well as of transition of actin subunits from "off" to
"on" state. CaD inhibits this significantly. Denervation atrophy inhibits the effect of S-1 as well but does not
affect the capability of CaD decreasing the formation of strong binding in actomyosin complex. It is supposed that
CaD "freezes" F-actin structure in "off" state. The denervation atrophy has no effect on CaD responsibility to bind
thin filaments and to switch "off" actin monomers.
