Escherichia coli RecX inhibits RecA recombinase and coprotease activities in vitro and in vivo

Elizabeth A. Stohl, Joel P. Brockman, Kristin L. Burkle, Katsumi Morimatsu, Stephen C. Kowalczykowski, H. Steven Seifert*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

150 Scopus citations


In Escherichia coli the RecA protein plays a pivotal role in homologous recombination, DNA repair, and SOS repair and mutagenesis. A gene designated recX (or oraA) is present directly downstream of recA in E. coli; however, the function of RecX is unknown. In this work we demonstrated interaction of RecX and RecA in a yeast two-hybrid assay. In vitro, substoichiometric amounts of RecX strongly inhibited both RecA-mediated DNA strand exchange and RecA ATPase activity. In vivo, we showed that recX is under control of the LexA repressor and is up-regulated in response to DNA damage. A loss-of-function mutation in recX resulted in decreased resistance to UV irradiation; however, overexpression of RecX in trans resulted in a greater decrease in UV resistance. Overexpression of RecX inhibited induction of two din (damage-inducible) genes and cleavage of the UmuD and LexA repressor proteins; however, recX inactivation had no effect on any of these processes. Cells overexpressing RecX showed decreased levels of P1 transduction, whereas recX mutation had no effect on P1 transduction frequency. Our combined in vitro and in vivo data indicate that RecX can inhibit both RecA recombinase and coprotease activities.

Original languageEnglish (US)
Pages (from-to)2278-2285
Number of pages8
JournalJournal of Biological Chemistry
Issue number4
StatePublished - Jan 24 2003

ASJC Scopus subject areas

  • Molecular Biology
  • Biochemistry
  • Cell Biology


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