Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 277, Issue 17, Pages 14417-14425Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M109915200
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- NCI NIH HHS [5-T32-CA09678, CA56542] Funding Source: Medline
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The prototypical bacterial RecA protein promotes recombination/repair by catalyzing strand exchange between homologous DNAs. While the mechanism of strand exchange remains enigmatic, ATP-induced cooperativity between RecA protomers is critical for its function. A human RecA homolog, human RAD51 protein (hRAD51), facilitates eukaryotic recombination/repair, although its ability to hydrolyze ATP and/or promote strand exchange appears distinct from the bacterial RecA. We have quantitatively examined the hRAD51 ATPase. The catalytic efficiency (k(cat)/K-m) of the hRAD51 ATPase was similar to50-fold lower than the RecA ATPase. Altering the ratio of DNA/hRAD51 and including salts that stimulate DNA strand exchange (ammonium sulfate and spermidine) were found to affect the catalytic efficiency of hRAD51. The average site size of hRAD51 was determined to be similar to3 nt (bp) for both single-stranded and double-stranded DNA. Importantly, hRAD51 lacks the magnitude of ATP-induced cooperativity that is a hallmark of RecA. Together, these results suggest that hRAD51 may be unable to coordinate ATP hydrolysis between neighboring protomers.
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