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The human Rad51 protein: polarity of strand transfer and stimulation by hRP‐A
Author(s) -
Baumann Peter,
West Stephen C.
Publication year - 1997
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/16.17.5198
Subject(s) - biology , stimulation , polarity (international relations) , microbiology and biotechnology , biophysics , biochemistry , neuroscience , cell
The human Rad51 protein is homologous to the Escherichia coli RecA protein and catalyses homologous pairing and strand transfer reactions in vitro . Using single‐stranded circular and homologous linear duplex DNA, we show that hRad51 forms stable joint molecules by transfer of the 5′ end of the complementary strand of the linear duplex to the ssDNA. The polarity of strand transfer is therefore 3′ to 5′, defined relative to the ssDNA on which hRad51 initiates filament formation. This polarity is opposite to that observed with RecA. Homologous pairing and strand transfer require stoichiometric amounts of hRad51, corresponding to one hRad51 monomer per three nucleotides of ssDNA. Joint molecules are not observed when the protein is present in limiting or excessive amounts. The human ssDNA binding‐protein, hRP‐A, stimulates hRad51‐mediated reactions. Its effect is consistent with a role in the removal of secondary structures from ssDNA, thereby facilitating the formation of continuous Rad51 filaments.