Swi5-Sfr1 protein stimulates Rad51-mediated DNA strand exchange reaction through organization of DNA bases in the presynaptic filament
Journal article, 2014

The Swi5-Sfr1 heterodimer protein stimulates the Rad51-promoted DNA strand exchange reaction, a crucial step in homologous recombination. To clarify how this accessory protein acts on the strand exchange reaction, we have analyzed how the structure of the primary reaction intermediate, the Rad51/single-stranded DNA (ssDNA) complex filament formed in the presence of ATP, is affected by Swi5-Sfr1. Using flow linear dichroism spectroscopy, we observe that the nucleobases of the ssDNA are more perpendicularly aligned to the filament axis in the presence of Swi5-Sfr1, whereas the bases are more randomly oriented in the absence of Swi5-Sfr1. When using a modified version of the natural protein where the N-terminal part of Sfr1 is deleted, which has no affinity for DNA but maintained ability to stimulate the strand exchange reaction, we still observe the improved perpendicular DNA base orientation. This indicates that Swi5-Sfr1 exerts its activating effect through interaction with the Rad51 filament mainly and not with the DNA. We propose that the role of a coplanar alignment of nucleobases induced by Swi5-Sfr1 in the presynaptic Rad51/ssDNA complex is to facilitate the critical matching with an invading double-stranded DNA, hence stimulating the strand exchange reaction.


Louise Fornander

Chalmers, Chemical and Biological Engineering, Physical Chemistry

A. Renodon-Corniere

Unite de Fonctionnalite et Ingenierie des Proteines

N. Kuwabara

University of Tokyo

High Energy Accelerator Research Organization

K. Ito

Tokyo Institute of Technology

Y. Tsutsui

Tokyo Institute of Technology

T. Shimizu

University of Tokyo

H. Iwasaki

Tokyo Institute of Technology

Bengt Nordén

Chalmers, Chemical and Biological Engineering, Physical Chemistry

M. Takahashi

Unite de Fonctionnalite et Ingenierie des Proteines

Nucleic Acids Research

0305-1048 (ISSN) 1362-4962 (eISSN)

Vol. 42 4 2358-2365

Supramolecular Motive Power (SUMO)

European Commission (FP7), 2009-01-01 -- 2014-12-31.

Subject Categories

Physical Chemistry



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