Effect of the C-terminal actin-binding sites of caldesmon on the interaction of actin with myosin |
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Authors: | Vikhorev P G Avrova S V Ermakov V S Copeland O Marston S B Borovikov Iu S |
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Institution: | Institute of Cytology RAS, St. Petersburg. |
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Abstract: | TRITC-phalloidin or FITC-labeled F-actin of ghost muscle fibers was bound to tropomyosin and C-terminal recombinant fragments of caldesmon CaDH1 (residues 506-793) or CaDH2 (residues 683-767). After that the fibers were decorated with myosin subfragment 1. In the absence of caldesmon fragments, subfragment 1 interaction with F-actin caused changes in parameters of polarized fluorescence, that were typical of "strong" binding of myosin heads to F-actin and of the "switched on" conformational state of actin. CaDH1 inhibited, whereas CaDH2 activated the effect of subfragment 1. It is suggested that C-terminal part of caldesmon may modulate the transition of F-actin subunits from the "switched on" to the "switched off" state. |
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