Caldesmon thin filament component

Apart from the phosphorylation theory, other regulatory mechanisms have also been suggested for smooth muscle contraction. A thin-filament protein that has been proposed as a regulatory component is caldesmon [102], Purified caldesmon is a potent inhibitor of actin-tropomyosin interaction with myosin. The mechanisms by which calcium removes this inhibition are controversial. Furthermore, phosphorylation of caldesmon by a caldesmon kinase in vitro has also been implicated in this... 

In vitro experimentation has shown that caldesmon is an integral component of smooth muscle thin filaments and plays a central role in their Ca2+-dependent regulation. A mechanism analogous to that of troponin has been proposed this now requires extensive testing. The structure of the regulatory domain of caldesmon is not well defined and we look forward to being able to describe this in three dimensions and in combination with its physiological partners actin, tropomyosin, and calmodulin. 

Fig. 5. Schematic representation of components of the thin filament of smooth muscle. Although calponin and caldesmon are both shown as components of the same filament, there is evidence that they may selectively associate with different actin isoforms in different populations of thin filaments...

Marston SB, Huber PA (1996) Caldesmon. In Barany M (ed)Biochemistry of smooth muscle contraction. Academic Press Inc. San Diego,California, pp 7790 Marston SB, Lehman W (1985) Caldesmon is a Ca -regulatory component of native smooth-muscle thin filaments. Biochem J 231 517522 Marston SB, Redwood CS (1991) The molecular anatomy of caldesmon. Biochem J 279 116... 

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