Meromyosin heavy

Huxley suggested that crossbridges can move out in this way and bind to actin because S-2 of HMM acted as a flexible link between LMM in the thick filament backbone and S-1. This was based on the observation that heavy meromyosin could be digested by chymotrypsin into two further subffagments (Lowey et al., 1966), S-1 and S-2, as described above, and that S-1 contained the ATPase and actin binding sites, whereas S-2 did not moreover, S-2 did not self-aggregate, as did the rod or LMM portion of myosin. 

Eisenberg, E. Moos, C. (1968). Adenosine triphosphate activity of acto-heavy meromyosin A kinetic analysis of actin activation. Biochemistry 7, 1486-1489. 

Trentham, D.R., Bardsley, R.G., Eccleston, J.F., Weeds, G. (1972). Elementary processes of the magnesium ion-dependent adenosine triphosphatase activity of heavy meromyosin. Biochem. J. 126, 635-644. 

Heavy meromyosin (HMM molecular mass about 340 kDa) is a soluble protein that has both a fibrous portion and a globular portion (Figure 49-4). It exhibits ATPase activity and binds to F-actin. Digestion of HMM with papain generates two subfragments, S-1 and S-2. The S-2 fragment is fibrous in character, has no ATPase activity, and does not bind to F-actin. 

The two ends of the F-actin filaments have different surfaces of the monomer exposed and grow at different rates. This has been demonstrated by allowing the myosin fragment called heavy meromyosin (HMM see Fig. 19-10) to bind to (or "decorate") an actin filament. The... 

Figure 19-10 (A) An approximate scale drawing of the myosin molecule. The "hinge" is a region that is rapidly attacked by trypsin to yield the light and heavy meromyosins (LMM and HMM). Total length -160 nm, molecular mass, 470 kDa two -200-kDa heavy chains two pairs of 16- to 21-kDa light chains heads -15 x 4 x 3 nm. (B) Electron micrograph of rabbit myosin monomers that became dissociated from thick filaments in the presence of ATP, fixed and shadowed with platinum.127 Courtesy of Tsuyoshi Katoh.

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],... 

Pato, M. D., Sellers, J. R, Preston, Y. A., Harvey, E. V., and Adelstein, R. S. (1996). Baculovirus expression of chicken nonmuscle heavy meromyosin II-B. Characterization of alternatively spliced isoforms./. Biol. Chem. 271, 2689-2695. 

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. 

King, G.J. and Holtrop, M.E. (1975) Actin-like filaments in bone cells of cultured mouse calvaria as demonstrated by binding to heavy meromyosin. Journal of Cell Biology 66 445-451... 

Figure 8.10 Schematic drawing of the myosin molecule. Note that trypsin produces two fragments, light and heavy meromyosins.

Eisenberg E, Moos C. Actin activation of heavy meromyosin adenosine triphosphatase. Dependence on adenosine triphosphate and actin concentrations. J. Biol. Chem. 1970 245 2451-2456. 

Figure 34.17. Watching a Single Motor Protein in Action. (A) An actin filament (blue) is placed above a heavy meromyosin (HMM) fragment (yellow) that projects from a bead on a glass slide. A bead attached to each end of the actin filament is held in an optical trap produced by a focused, intense infrared laser beam (orange). The position of these beads can be measured with nanometer precision. (B) Recording of the displacement of the actin filament induced by the addition of ATP. [After J. T. Finer, R. M. Simmons, and J. A. Spudich. Nature 368(1994) 113.]...

It is of interest that the Si subfragment, the head of the myosin molecule, does not induce any aggregation in the presence of connectin (Maruyama et al., 1985a). However, heavy meromyosin interacted with connectin to form aggregates. The neck portion S2 of myosin did not act on connectin. L-Meromyosin and the rod portion of myosin were markedly... 

When ATP and 2,4,6-trinitrobenzenesulphonic acid are mixed at pH 9.5, 2 - (or 3 -) 0-(2,4,6-trinitrophenyl)adenosine-5 -triphosphate (22) is formed, which binds to, and is hydrolysed by, heavy meromyosin. This ATP derivative exhibits reversible formation of a Meisenheimer complex, with pK 5.1. The... 

Other Polyphosphates.—The hydrolysis of the fluorescent l,A -ethenoadeno sine triphosphate (28) by myosin, and the fluorescence change observed on binding to heavy meromyosin, have been investigated, along with equili-... 

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