Effect of Nucleotide Cofactor Structure on RecA Protein-Promoted DNA Pairing. 1. Three-Strand Exchange Reaction

Karen L. Menge, Floyd R. Bryant

Research output: Contribution to journalArticlepeer-review

Abstract

The structurally related nucleoside triphosphates, adenosine triphosphate (ATP), purine riboside triphosphate (PTP), inosine triphosphate (ITP), and guanosine triphosphate (GTP), are all hydrolyzed by the recA protein with the same turnover number (17.5 min-1). The S0.5 values for these nucleotides increase progressively in the order ATP (45 µM), PTP (100 µM), ITP (300 µM), and GTP (750 µM). PTP, ITP, and GTP are each competitive inhibitors of recA protein-catalyzed ssDNA-dependent ATP hydrolysis, indicating that these nucleotides all compete for the same catalytic site on the recA protein. Despite these similarities, ATP and PTP function as cofactors for the recA protein-promoted three-strand exchange reaction, whereas ITP and GTP are inactive as cofactors. The strand exchange activity of the various nucleotides correlates directly with their ability to support the isomerization of the recA protein to a strand exchange-active conformational state. The mechanistic deficiency of ITP and GTP appears to arise as a consequence of the hydrolysis of these nucleotides to the corresponding nucleoside diphosphates, IDP and GDP. We speculate that nucleoside triphosphates with S0.5 values greater than 100 µM will be intrinsically unable to sustain the strand exchange-active conformational state of the recA protein during ongoing NTP hydrolysis and will therefore be inactive as cofactors for the strand exchange reaction.

Original languageEnglish (US)
Pages (from-to)5151-5157
Number of pages7
JournalBiochemistry
Volume31
Issue number22
DOIs
StatePublished - Feb 1 1992

ASJC Scopus subject areas

  • Biochemistry

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