Functional similarities between phage lambda Orf and Escherichia coli RecFOR in initiation of genetic exchange

Proc Natl Acad Sci U S A. 2005 Aug 9;102(32):11260-5. doi: 10.1073/pnas.0503399102. Epub 2005 Aug 2.

Abstract

Genetic recombination in bacteriophage lambda relies on DNA end processing by Exo to expose 3'-tailed strands for annealing and exchange by beta protein. Phage lambda encodes an additional recombinase, Orf, which participates in the early stages of recombination by supplying a function equivalent to the Escherichia coli RecFOR complex. These host enzymes assist loading of the RecA strand exchange protein onto ssDNA coated with ssDNA-binding protein. In this study, we purified the Orf protein, analyzed its biochemical properties, and determined its crystal structure at 2.5 angstroms. The homodimeric Orf protein is arranged as a toroid with a shallow U-shaped cleft, lined with basic residues, running perpendicular to the central cavity. Orf binds DNA, favoring single-stranded over duplex and with no obvious preference for gapped, 3'-tailed, or 5'-tailed substrates. An interaction between Orf and ssDNA-binding protein was indicated by far Western analysis. The functional similarities between Orf and RecFOR are discussed in relation to the early steps of recombinational exchange and the interplay between phage and bacterial recombinases.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacteriophage lambda / genetics*
  • Blotting, Western
  • Cloning, Molecular
  • Crystallography
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Escherichia coli / genetics*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Models, Molecular*
  • Molecular Sequence Data
  • Recombination, Genetic / genetics*
  • Sequence Analysis, DNA
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*

Substances

  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • RecO protein, E coli
  • RecR protein, E coli
  • Viral Proteins
  • recF protein, E coli

Associated data

  • PDB/1PC6