Actin thin filament-linked regulation

A family of actin-binding proteins that exist in various isoforms. As with other protein isoforms or isoenzymes, the expression of the isoforms is tissue-specific. The interaction of calponin with actin inhibits the actomyosin Mg-ATRase activity. See Winder, S. and Walsh, M., Inhibition of the actinomyosin MgATRase by chicken gizzard calponin. Prog. Clin. Biol. Res. 327, 141-148, 1990 Winder, S.J., Sutherland, C., and Walsh, M.R., Biochemical and functional characterization of smooth muscle calponin, Adv. Exp. Med. Biol. 304, 37-51, 1991 Winder, S.J. and Walsh, M.R., Calponin thin filament-linked regulation of smooth muscle contraction. Cell Signal. 5,677-686,1993 el-Mezgueldi, M., Calponin, Int. J. Biochem. 

As discussed above one important function of caldesmon appears to be in a thin filament associated regulatory system. In addition, caldesmon binds to myosin (Ikebe and Reardon 1988) and can cross-link and tether actin to myosin (Haeberle et al. 1992) and may possibly also have role in stabilising the thick filaments (Katayama et al. 1995). The regulation of these processes in the smooth muscle fibre is unknown. 

Major component of the thin filaments. Actin is an impotant cytoskeletal protein in non-muscle cells. Six human isoforms are known Cross-links actin at the Z disks Caps the plus ends of actin filaments at the Z-disk Thin filament regulation in smooth muscle... 

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