Reference - PMID:22033972 - Fission yeast Swi5-Sfr1 protein complex, an activator of Rad51 recombinase, forms an extremely elongated dogleg-shaped structure.
Reference summary
- PubMed ID
- PMID:22033972
- Title
- Fission yeast Swi5-Sfr1 protein complex, an activator of Rad51 recombinase, forms an extremely elongated dogleg-shaped structure.
- Authors
- Kokabu Y, Murayama Y, Kuwabara N, Oroguchi T, Hashimoto H, Tsutsui Y, Nozaki N, Akashi S, Unzai S, Shimizu T, Iwasaki H, Sato M, Ikeguchi M
- Citation
- J Biol Chem 2011 Dec 16;286(50):43569-76
- Publication year
- 2011
- 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.
