Combining Electron Microscopy and X-Ray Crystallography Data to Study the Structure of F-Actin and its Implications for Thin-Filament Regulation In Muscle
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Actin filaments (F-actin) are found in nearly all eukaryotic cells as elements of the cytoskeleton. They also play a central role in various types of contractility, motility and transport. F-actin is a helical polymer composed of identical globular subunits, each of which contains 375 amino acids. The atomic structure of the monomer (G-actin; 42 kD) has recently been determined from a complex of the monomer and DNase (Kabsch et al., 1990). The monomer structure, shown in figure 1, has two major domains (historically these were termed “large” and “small”, but it is now known that they are of nearly the same size) which are each divided into two subdomains. Subdomain 1 contains the N- and C-termini of the polypeptide chain. The prominent cleft between the two major domains is the site of nucleotide binding. Knowledge of the precise arrangement of the actin subunits within F-actin would be helpful in understanding the function of F-actin at the molecular level.
KeywordsActin Filament Thin Filament Helix Axis Fluorescence Energy Transfer Myosin Subfragment
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- Geeves, M.A. and Halsall, D.J., 1987, Two step ligand binding and cooperativity, Biophys. J. 52: 215.Google Scholar
- Hartt, J. E. and Mendelson, R.A., 1980, X-Ray scattering of F-actin and myosin subfragment 1 complex, Fed. Proc. 39: 1728.Google Scholar
- Lehrer, S.S. and Morris, E.P., 1984, Dual effects of tropomyosin and tropomyosin-troponin on acto-myosin subfragment 1 ATPase, J. Biol. Chem. 257: 8073.Google Scholar
- Mendelson, R.A., Gebhard, W., Holmes, K., Kabsch, W., Suck, D., Couch, J., Morris, E. and O’Brien, E., 1984, Fitting the actin monomer into the actin helix: a combination of X-ray diffraction and electron microscope data, Biophys. J. 45: 391a.Google Scholar
- Mendelson, R.A., Stone, D.B., Timmins, P.A., and Johnson, E.R., 1991, Results of preliminary studies of tropomyosin radial movement using neutron scattering, Biophys. J. 59: 219a.Google Scholar
- Morris, E.P., 1979, The effects of troponin components on the structure and activity of thin filaments, Ph. D. thesis, University of London.Google Scholar
- O’Brien, E.J., Couch, J., Johnson, G.R.P., and Morris, E.P., 1983, Structure of actin and the thin filament, in: “Actin: Its Structure and Function in Muscle and Non-muscle Cells” C. Dos Remedios and J. Barden, editors, Academic Press, Sydney, Australia.Google Scholar