Actin subfragment

Myosin Subfragment-1 Interacts With Two G-Actin Molecules... 

Combeau, C., Didry, D., Carlier. M.-F. (1992). Interaction between G-actin and myosin subfragment-I probed by covalent crosslinking. J. Biol. Chem. 267, 14038-14046. 

Fievez, S. Carlier, M.-F. (1993). Conformational changes in subdomain-2 of G-actin upon polymerization into F-actin and upon binding myosin subfragment-1. FEES Lett. 316, 186-190. 

Miller, L., Phillips, M Reisler, E. (1988). Polymerization of G-actin by myosin subfragment-1. J. Biol. Chem. 263, 1996-2002. 

Figure 14. Crystal structures of actin and myosin subfragment-1, shown to the same scale.

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. 

Miki M, Dosremedios CG (1988) Fluorescence quenching studies of fluorescein attached to Lys-61 or Cys-374 in actin effects of polymerization, myosin subfragment-1 binding, and tropomyosin-troponin binding. J Biochem Tokyo 104 232-235... 

Iodoacetyl-LC-biotin has been used to localize the SH thiol of myosin by use of an avidin-biotin complex visualized by electron microscopy (Sutoh et al., 1984) and to determine the spatial relationship between SHj and the actin binding site on the myosin subfragment-1 surface (Yamamoto et al., 1984). 

Aguirre, R., Gonsoulin, F., and Cheung, H.C. (1986) Interaction of fluorescently labelled myosin subfragment 1 with nucleotide and actin. Biochemistry 25, 6827. 

Labbe, J.R, Mornet, D., Roseau, G., and Kassab, R. (1982) Cross-linking of F-actin to skeletal muscle myosin subfragment 1 with bis(imido esters) Further evidence for the interaction of myosin-head heavy chain with an actin dimer. Biochemistry 21, 6897-6902. 

Yamamoto, K., Sekine, T., and Sutoh, K. (1984) Spatial relationship between SHI and the actin binding site on myosin subfragment-1 surface. FEES Lett. 176, 75-78. 

Figure 4.5. Structure of myosin. Myosin comprises both light and heavy chains. The heavy chains may be cleaved by trypsin to generate light meromyosin (LMM) and heavy mero-myosin (HMM). Papain digestion of HMM yields subfragments SI and S2 each SI fragment contains an ATPase site and an actin-binding site. The light chains modify the activity of the ATPase.

White et aP measured the rates of phosphate release during a single turnover of actomyosin nucleoside triphosphate (NTP) hydrolysis using a double-mixing stopped-flow spectrofluorometer, at very low ionic strength to increase the affinity of myosin-ATP and myo-sin-ADP-Pi to actin. Myosin subfragment 1 and a series of nucleoside triphosphates were mixed and incubated for approximately 1-10 s to allow NTP to bind to myosin and generate a steady-state mixture of myosin-NTP and myosin-NDP-Pi. The steady-state intermediates were then mixed with actin. 

Greene, L. E. (1986) Cooperative binding of myosin subfragment one to regulated actin as measured by fluoresce changes of troponin 1 modified within different fluorophores. J. Biol. Chem. 261, 1279. 

Lehrer, S. S., Golitsina, N. L., and Geeves, M. A. (1997). Actin-tropomyosin activation of myosin subfragment 1 ATPase and thin filament cooperativity. The role of tropomyosin flexibility and end-to-end interactions. Biochemistry 36, 13449-13454. 

McKillop, D. F. A., and Geeves, M. A. (1993). Regulation of the interaction between actin and myosin subfragment 1 Evidence for three states of the thin filament. Biophys. J. 65, 693-701. 

Criddle, A. H., Geeves, M. A., andjeffries, T. (1985). The use of actin labeled with N-(l-pyrenyl)iodoacetamide to study the interaction of actin with myosin subfragments and troponin/tropomyosin. Biochem. J. 232, 343-349. 

Margossian, S. S., and Lowey, S. (1973b). Substructure of the myosin molecule. IV. Interactions of myosin and its subfragments with adenosine triphosphate and actin. / Mol. Biol. 74, 313-330. 

Millar, N. C., and Geeves, M. A. (1983). The limiting rate of the ATP-mediated dissociation of actin from rabbit skeletal muscle myosin subfragment 1. FEES Lett. 160, 141-148. 

Neibling, C.Toyoshima and J.A. Spudich,"Myosin Subfragment-1 is Sufficient to Move Actin Filaments in vitro, Nature 328, 536, 1987 ... 

FIGURE 8 Kinetic scheme for the hydrolysis of ATP by smooth muscle actomyosin. M = myosin (or its subfragments) A = actin T = ATP D = ADP Pi = inorganic phosphate. 

The unusually large number of residues that are necessary to form a stable-coiled-coil region (>180) raises the possibility that a "loose" subfragment-2 region of the molecule may be important for some function of myosin. If all myosin rods show this instability, then a possible role may be to introduce enough flexibility at the region where the heads join so that both heads of myosin can bind equivalently to actin. 

It is useful to first consider the structure of muscle s mechanochemical transduction elements, actin and the subfragment-1 (S-1) portion of myosin, before analyzing the effects of regulatory proteins that modulate interactions of the two and have the potential therefore to control force generation. Molecular details of the structure of skeletal muscle actin (Kabsch et al, 1990 Holmes and Kabsch, 1991 Lorenz et al., 1993) and S-1 (Rayment etal., 1993a) are known at the atomic level (Fig. 1), and given the general similarity of F-actin and S-1 in smooth and in skeletal muscle, it is reasonable to assume that they are closely related in the two... 

Current studies suggest a vital role for CaD in the regulation of smooth muscle contraction since it inhibits the actin-activated ATPase activity of myosin (Da-browska et al., 1985 Smith and Marston, 1985 Moody et al., 1985 Sobue et al., 1985) and its subfragments (Lash et al., 1986 Chalovich et al., 1987). However, defining the precise role of CaD in cells requires an understanding of its interaction with several key proteins, namely, actin, myosin, calmodulin, and caltropin. 

---