H-Meromyosin

Myosin. Rabbit muscle myosin is a long, thin molecule (VI400 X 20-50 A) with a molecular weight of 5 X 10. It is composed of two heavy chains and four light chains as demonstrated by SDS-polyacrylamide disc gel electrophoresis. On tryptic digestion, myosin is split into the subunits, H-meromyosin (HMM) and L-mero-myosin (LMM). HMM is further split into S-l and S-2 subunits. While LMM is a rod of V)0% a-helical content, the a-helical content for HMM, S-l and S-2 fragments is 46%, 33% and 87%, respectively. The ATPase activity is localized in the S-l subunit (33,34). Although fish myosins appear to have the same structural profile (10,22,35-40) and similar amino acid composition as rabbit myosin (39,41,42), fish myosin is different from rabbit myosin in physicochemical properties such as solubility, viscosity and stability (10,22,35-40). 

Similar studies were performed on the subunits L-meromyosin and H-meromyosin. In the former 90 % of the phenolic groups appear abnormal, but they are titrated normally in 5 M urea. In H-meromyosin all of the groups are normal, even in aqueous solution. 

Subunits of Myosin. Matsumoto et al. (64) isolated H-meromyosin (HMM) and L-meromyosin (LMM) from carp muscle (15) and studied their stabilities at — 20°C. The ATPase activity of HMM decreased much faster than that of myosin and the capacity of HMM to bind with F-actin as determined by electron microscopy was lost. LMM also exhibited a decreased capacity to form well-ordered paracrystals. These results tend to indicate that frozen storage causes myosin molecules to aggregate side-by-side and myosin subunits to undergo conformational deformations. 

Onishi, H., Maeda, K., Maeda, Y., Inoue, A., and Fujiwara, K. (1995). Functional chicken gizzard heavy meromyosin expression in and purification from baculovirus-infected insect cells. Proc. Natl. Acad. Sci. USA 92, 704-708. [Published erratum appears in Proc. Natl. Acad. Sci. USA 1995 92, 3076],... 

Warshaw, D. M., Guilford, W. H., Freyzon, Y., Krementsova, E., Palmiter, K. A., Tyska, M. J., Baker, J. E., and Trybus, K. M. (2000). The light chain binding domain of expressed smooth muscle heavy meromyosin acts as a mechanical lever./. Biol. Chem. 275, 37167-37172. 

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... 

Oplatka, A. Borejdo, J. Gadasi, H. Tension development in stretched glycerin-ated muscle fibers and contraction of ghost myofibrils induced by irrigation with heavy meromyosin. FEES Lett. 1974, 45, 55-58. 

Oplatka, A. Gadasi, H. Borejdo, J. The contraction of ghost myofibrils and glycerinated muscle fibers irrigated with heavy meromyosin subffagment-1. Biochem. Biophys. Res. Commun. 1974, 58, 905-912. 

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