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Crystallographic conformers of Actin in a biologically active bundle of filaments

Cong, Y. and Topf, Maya and Sali, A. and Matsudaira, P. and Dougherty, M. and Chiu, W. and Schmid, M.F. (2008) Crystallographic conformers of Actin in a biologically active bundle of filaments. Journal of Molecular Biology 375 (2), pp. 331-336. ISSN 0022-2836.

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Actin carries out many of its cellular functions through its filamentous form; thus, understanding the detailed structure of actin filaments is an essential step in achieving a mechanistic understanding of actin function. The acrosomal bundle in the Limulus sperm has been shown to be a quasi-crystalline array with an asymmetric unit composed of a filament with 14 actin–scruin pairs. The bundle in its true discharge state penetrates the jelly coat of the egg. Our previous electron crystallographic reconstruction demonstrated that the actin filament cross-linked by scruin in this acrosomal bundle state deviates significantly from a perfect F-actin helix. In that study, the tertiary structure of each of the 14 actin protomers in the asymmetric unit of the bundle filament was assumed to be constant. In the current study, an actin filament atomic model in the acrosomal bundle has been refined by combining rigid-body docking with multiple actin crystal structures from the Protein Data Bank and constrained energy minimization. Our observation demonstrates that actin protomers adopt different tertiary conformations when they form an actin filament in the bundle. The scruin and bundle packing forces appear to influence the tertiary and quaternary conformations of actin in the filament of this biologically active bundle.

Item Type: Article
Keyword(s) / Subject(s): Actin, electron cryomicroscopy, acrosomal bundle, energy minimization, conformational heterogeneity
School or Research Centre: Birkbeck Schools and Research Centres > School of Science > Biological Sciences
Depositing User: Administrator
Date Deposited: 04 Aug 2010 14:09
Last Modified: 11 Oct 2016 12:01

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