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A model for dsDNA translocation revealed by a structural motif common to RecG and Mfd proteins.

Mahdi, A.A.; Briggs, G.S.; Sharples, G.J.; Wen, Q.; Lloyd, R.G.

Authors

A.A. Mahdi

G.S. Briggs

Q. Wen

R.G. Lloyd



Abstract

RecG protein differs from other helicases analysed to atomic resolution in that it mediates strand separation via translocation on double-stranded (ds) rather than single-stranded (ss) DNA. We describe a highly conserved helical hairpin motif in RecG and show it to be important for helicase activity. It places two arginines (R609 and R630) in opposing positions within the component helices where they are stabilized by a network of hydrogen bonds involving a glutamate from helicase motif VI. We suggest that disruption of this feature, triggered by ATP hydrolysis, moves an adjacent loop structure in the dsDNA-binding channel and that a swinging arm motion of this loop drives translocation. Substitutions that reverse the charge at R609 or R630 reduce DNA unwinding and ATPase activities, and increase dsDNA binding, but do not affect branched DNA binding. Sequences forming the helical hairpin and loop structures are highly conserved in Mfd protein, a transcription-coupled DNA repair factor that also translocates on dsDNA. The possibility of type I restriction enzymes and chromatin-remodelling factors using similar structures to drive translocation on dsDNA is discussed.

Citation

Mahdi, A., Briggs, G., Sharples, G., Wen, Q., & Lloyd, R. (2003). A model for dsDNA translocation revealed by a structural motif common to RecG and Mfd proteins. The EMBO Journal, 22, 724-734

Journal Article Type Article
Publication Date 2003
Journal EMBO Journal
Print ISSN 0261-4189
Publisher EMBO Press
Volume 22
Pages 724-734
Publisher URL http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12554672