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Title
Japanese: 
English:Fission yeast Swi5-Sfr1 protein complex, an activator of Rad51 recombinase, forms an extremely elongated dogleg-shaped structure 
Author
Japanese: Kokabu, Y., 村山泰斗, Kuwabara, N., Oroguchi, T., Hashimoto, H., 筒井康博, Nozaki, N., Akashi, S., Unzai, S., Shimizu, T., 岩崎博史, Sato, M., Ikeguchi, M..  
English: Kokabu, Y., Yasuto Murayama, Kuwabara, N., Oroguchi, T., Hashimoto, H., Yasuhiro Tsutsui, Nozaki, N., Akashi, S., Unzai, S., Shimizu, T., Hiroshi Iwasaki, Sato, M., Ikeguchi, M..  
Language English 
Journal/Book name
Japanese:Journal of Biological Chemistry 
English:Journal of Biological Chemistry 
Volume, Number, Page Vol. 286    No. 50    pp. 43569-43576
Published date Dec. 2011 
Publisher
Japanese: 
English: 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
Official URL http://www.scopus.com/inward/record.url?eid=2-s2.0-83355174043&partnerID=MN8TOARS
 
DOI https://doi.org/10.1074/jbc.M111.303339
Abstract In eukaryotes, DNA strand exchange is the central reaction of homologous recombination, which is promoted by Rad51 recombinases forming a right-handed nucleoprotein filament on single-stranded DNA, also known as a presynaptic filament. Accessory proteins known as recombination mediators are required for the formation of the active presynaptic filament. One such mediator in the fission yeast Schizosaccharomyces pombe is the Swi5-Sfr1 complex, which has been identified as an activator of Rad51 that assists in presynaptic filament formation and stimulates its strand exchange reaction. Here, we determined the 1:1 binding stoichiometry between the two subunits of the Swi5-Sfr1 complex using analytical ultracentrifugation and electrospray ionization mass spectrometry. Small-angle x-ray scattering experiments revealed that the Swi5-Sfr1 complex displays an extremely elongated dogleg-shaped structure in solution, which is consistent with its exceptionally high frictional ratio (f/f(0)) of 2.0 ± 0.2 obtained by analytical ultracentrifugation. Furthermore, we determined a rough topology of the complex by comparing the small-angle x-ray scattering-based structures of the Swi5-Sfr1 complex and four Swi5-Sfr1-Fab complexes, in which the Fab fragments of monoclonal antibodies were specifically bound to experimentally determined sites of Sfr1. We propose a model for how the Swi5-Sfr1 complex binds to the Rad51 filament, in which the Swi5-Sfr1 complex fits into the groove of the Rad51 filament, leading to an active and stable presynaptic filament.

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