[Caldesmon and calponin are proteins, participating in the regulation of myosin and actin interaction in nonmuscle and smooth muscle cells].

The structure and properties of two novel regulatory proteins of nonmuscle cells and smooth muscles are reviewed. The localization of the "light" caldesmon isoform in nonmuscle cells and the involvement of this protein in the formation of cytoskeleton structures are described. A detailed description of the "heavy" caldesmon isoform and of localization of sites of caldesmon interaction with actin, tropomyosin, myosin and calmodulin, is given. The data on caldesmon phosphorylation by protein kinases are reviewed. Some present-day concepts concerning the mechanism of caldesmon function during regulation of myosin interaction with actin are considered. The structure, properties and phosphorylation of calponin are described. The properties of calponin and caldesmon are compared with those of troponin components involved in the regulation of the contractile activity of striated muscles.