A mutation in helicase motif III of E. coli RecG protein abolishes branch migration of Holliday junctions.

Sharples, G.J.; Whitby, M.C.; Ryder, L.; Lloyd, R.G.

Abstract

The RecG protein of Escherichia coli catalyses branch migration of Holliday junctions made by RecA and dissociates synthetic X junctions into duplex products in reactions that require hydrolysis of ATP. To investigate the mode of action of this enzyme a chromosomal mutation that inactivates recG (recG162) was cloned and sequenced. The recG162 mutation is a G:C to A:T transition, which produces an Ala428 to Val substitution in the protein. This change affects a motif (motif III) in the protein that is highly conserved in DNA and RNA helicases. RecG162 protein was purified and shown to retain the ability to bind synthetic X and Y junctions. However, it does not dissociate these junctions and fails to catalyse branch migration of Holliday junction intermediates purified from a RecA strand exchange reaction. RecG162 retains a DNA-dependent ATPase activity, but this is much reduced relative to the wild-type protein, especially with single-stranded DNA as a co-factor. These results suggest that branch migration by RecG is related to a junction-targeted DNA helicase activity.

Citation

Sharples, G., Whitby, M., Ryder, L., & Lloyd, R. (1994). A mutation in helicase motif III of E. coli RecG protein abolishes branch migration of Holliday junctions. Nucleic Acids Research, 22(3), 308-313

• Journal Article Type: Article
• Publication Date: 1994
• Journal: Nucleic Acids Research
• Print ISSN: 0305-1048
• Publisher: Oxford University Press
• Volume: 22
• Issue: 3
• Pages: 308-313
• Publisher URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=8127666