Myosin heavy chain phosphorylation

Myosin-I molecules have several IQ sequences on or near the head and have light chains associated with them (Cheney and Mooseker, 1992 Cheney et al., 1993). Frequently, the light chains appear to be calmodulin molecules and some myosin-I molecules can bind three to four molecules of calmodulin at one time. Brush-border and adrenal myosin-I also bind calmodulin. Acanthamoeba myosin-I has a light chain that can be removed, in vitro, without adversely affecting the ATPase activity or the heavy chain phosphorylation (Korn and Hammer, 1988). The role of these calmodulin molecules in regulating myosin-I is complex and poorly understood. One possibility is that the calmodulin molecules dissociate from the heavy chains when calcium binds to the calmodulin, thereby imparting greater flexibility to the head of the myosin-I molecules. 

Li X, Zhou L, and Gorodeski GI [2006] Estrogen regulates epithelial cell deformability by modulation of cortical acto-myosin through phosphorylation of non-muscle myosin-heavy-chain II-B filaments. Endocrinology 147 5236-5248... 

S ATP -I- myosin I heavy chain <1, 2, 9-11> (<10> major site of phosphorylation is Ser8 [22] <2> 35 kDa trypsin fragment of the C-terminus of the maximally activated, phosphorylated enzyme is fully catalytically active and contains 2 thirds of the autophosphorylation sites of the native enzyme [20] <9,10> substrate myosin ID [19,22] <2> higher activity with membrane-bound substrate myosin I [17] <2> substrates are heavy chains of myosin lA and IB [6,7,17] <2,11> substrate is heavy chain of myosin IC [7,23,24] <2> a basic amino acid is essential on amino-terminal side of phosphorylation site, two are preferable, and a Tyr-residue is essential two residues away on the COOH-terminal side [7] <2> contains two myosin heavy chain kinases one for myosin I and one for myosin II... 

Brzeska, H., and Korn, E. D. (1996). Regulation of class I and class II myosins by heavy chain phosphorylation. / Biol. Chem. 271, 16983-16986. 

Fujita-Becker, S., Durrwang, U., Erent, M., Clark, R. J., Geeves, M. A., and Manstein, D. J. (2005). Changes in Mg2+-ion concentration and heavy chain phosphorylation regulate the motor activity of a class-I myosin. / Biol. Chem. 280, 6064-6071. 

Adelstein, R. S. (1993). Phosphorylation of vertebrate nonmuscle and smooth muscle myosin heavy chains and light chains. Mol. Cell Biochem. 127-128, 219-227. 

B. Phosphorylation of Smooth Muscle Myosin Heavy Chains... 

Katayama E, Scott-Woo G, Ikebe M (1995) Effect of caldesmon on the assembly of smooth muscle myosin. J Biol Chem 270 39193925 Kelley CA, Kawamoto S, Conti MA, Adelstein RS (1991) Phosphorylation of vertebrate smooth muscle and nonmuscle myosin heavy chains in vitro and in intact cells. J Cell Sci Suppl 14 4954... 

Nishikawa M, Hidaka H, Adelstein RS (1983) Phosphorylation of smooth muscle heavy meromyosin by calcium-activated, phospholipid-dependent protein kinase. The effect on actin-activated MgATPase activity. J Biol Chem 258 14069-1 2 Nishikori K, Weisbrodt NW, Sherwood OD, Sanborn BM (1983) Effects of relaxin on rat uterine myosin light chain kinase activity and myosin light chain phosphorylation. J Biol Chem 258 2468-2474... 

Kelley CA, Oberman F, Yisraeli JK, Adelstein RS (1995) A Xenopus nonmuscle myosin heavy chain isoform is phosphorylated by cyclin-p34 " kinase during meiosis. J Biol Chem 270 1395-1401... 

Heid, R, Geiger, J., Wessels, D., Voss, E., and SoU, D. R. (2005). Computer assisted analysis of filopod formation and the role of myosin II heavy chain phosphorylation in Dictyostelium. J. Cell Sci. 118, 2225-2237... 

Contraction in amoeboid cells makes use of nonmuscle forms of myosin type II whieh form bipolar thiek filaments in the cytoplasm and in association with the actin filaments [23, 54]. In Dictyostelium, actin filaments form a eortieal shell directly under the plasma membrane, with random orientation of the filaments [132]. Activation of myosin contractile activity by phosphorylation of the myosin light ehain protein results in contraction of the cortical network [54, 110], It is unclear whether this contraetion is uniform throughout the eell or whether there is spatial regulation of the activity. In polarized motile Dictyostelium cells, myosin is concentrated at the rear of the cell [31], which could maintain the polarization, while a myosin heavy chain kinase (which phosphorylates the myosin heavy chain protein and inhibits thick filament formation), is localized at the front of the cell. 

Rahmsdorf, H.J., Malchow, D. and Gerisch, G. (1978). Gyclic AMP-induced phosphorylation in Dictyostelium of a polypeptide comigrating with myosin heavy chains. FEBS Lett. 88, 322-326. 

Myosin-II phosphorylation is also an important mechanism for regulating myosin assembly in nonmuscle and smooth muscle cells (Kom and Hammer, 1988). For example, myosin-II ixomAcanthamoeba is more soluble when the heavy chain is phosphorylated compared to the unphosphorylated species. Similarly, phosphorylation of the light chains of vertebrate smooth muscle and nonmuscle myosin-II affects filament formation by these myosins. These myosins undergo a... 

The regulation of myosin-I activity is not well understood. As mentioned above, the heavy chain is phosphorylated in Acanthamoeba but the regulatory effect of this process is unclear. Myosin-I from Acanthamoeba, Dictyostelium, brush-bor-... 

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