RecBCD

Whitehouse, I., Stockdale, C., Flaus, A., Szczelkun, M.D., and Owen-Hughes, T. (2003) Evidence for DNA translocation by the ISWI chromatin-remodeling enzyme. Mol. Cell. Biol. 23, 1935-1945. Bianco, P.R., Brewer, L.R., Corzett, M., Balhorn, R., Yeh, Y., Kowalczykowski, S.C., and Baskin, R.J. (2001) Processive translocation and DNA unwinding by individual RecBCD enzyme molecules. Nature 409, 374-378. 

Enzymes that promote various steps of homologous recombination have been isolated from both prokaryotes and eukaryotes. In E. coli, the recB, recC, and recD genes encode the RecBCD enzyme, which has both he-licase and nuclease activities. The RecA protein pro-... 

FIGURE 25-37 Models for recombinational DNA repair of stalled replication forks. The replication fork collapses on encountering a DNA lesion (left) or strand break (right). Recombination enzymes promote the DNA strand transfers needed to repair the branched DNA structure at the replication fork. A lesion in a single-strand gap is repaired in a reaction requiring the RecF, RecO, and RecR proteins. Double-strand breaks are repaired in a pathway requiring the RecBCD enzyme. Both pathways require RecA. Recombination intermediates... 

Shen, P. Huang, H.V. (1993). Effect of base-pair mismatches on recombination via the RecBCD pathway. Molec. Gen. Genetics 218, 358-360. 

Singleton, M. R, Dillinigham, M. S., Gaudier, M., Kowalczykowski, C.. and Wigley, D. B. 2004, Crystal structure of RecBCD enzyme reveals a machine for processing DNA breaks. Nature... 

Exonuclease V (also called RecBCD nuclease) - A protein in E. coli recombination that binds at a double-strand break on duplex DNA and uses a helicase activity to unwind and partially degrade the DNA. It helps to load RecA to a 3 end. Figure 25.28... 

Figure 25.28 A model for the action of RecBCD, Chi sites, and RecA in initiating homologous recombination. 

Dohoney, KM and Gelles, J, Chi-sequence recognition and DNA translocation by single RecBCD helicase/nuclease molecules.Nature409 (2001) 370-374. 

Mutation abolishes homologous recombination and increases the stability of certain cloned DNA sequences. Strains grow more slowly and transform at lower efficiencies Structural genes for the subunits of exonuclease V. Mutant strains show deficiency in RecBCD enzyme-dependent recombination and DNA repair. Useful for stabilizing certain cloned DNA sequences, especially inverted repeat sequences. Strains grow slowly and are difficult to transform Mutation in exonuclease involved in a plasmid-by-plasmid homologous recombination... 

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