Nucleic Acids Research Advance Access originally published online on August 21, 2009
Nucleic Acids Research 2009 37(18):6042-6053; doi:10.1093/nar/gkp680
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Nucleic Acids Research, 2009, Vol. 37, No. 18 6042-6053
© The Author 2009. Published by Oxford University Press.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses?by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Genome Integrity, Repair and Replication |
An N-terminal clamp restrains the motor domains of the bacterial transcription-repair coupling factor Mfd
1Department of Chemistry, 2Department of Biochemistry & Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA and 3DNA-protein Interactions Unit, Department of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
*To whom correspondence should be addressed. Tel: +1 413 577 2890; Fax: +1 413 545 3291; Email: theis{at}biochem.umass.edu
Received June 25, 2009. Revised July 30, 2009. Accepted August 1, 2009.
Motor proteins that translocate on nucleic acids are key players in gene expression and maintenance. While the function of these proteins is diverse, they are driven by highly conserved core motor domains. In transcription-coupled DNA repair, motor activity serves to remove RNA polymerase stalled on damaged DNA, making the lesion accessible for repair. Structural and biochemical data on the bacterial transcription-repair coupling factor Mfd suggest that this enzyme undergoes large conformational changes from a dormant state to an active state upon substrate binding. Mfd can be functionally dissected into an N-terminal part instrumental in recruiting DNA repair proteins (domains 1–3, MfdN), and a C-terminal part harboring motor activity (domains 4–7, MfdC). We show that isolated MfdC has elevated ATPase and motor activities compared to the full length protein. While MfdN has large effects on MfdC activity and thermostability in cis, these effects are not observed in trans. The structure of MfdN is independent of interactions with MfdC, implying that MfdN acts as a clamp that restrains motions of the motor domains in the dormant state. We conclude that releasing MfdN:MfdC interactions serves as a central molecular switch that upregulates Mfd functions during transcription-coupled DNA repair.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.