Ku is central to the non-homologous end-joining pathway of double-strand-break repair in all three major domains of life, with eukaryotic homologues being associated with more diversified roles compared with prokaryotic and archaeal homologues. Ku has a conserved central ‘ring-shaped’ core domain. While prokaryotic homologues lack the N- and C-terminal domains that impart functional diversity to eukaryotic Ku, analyses of Ku from certain prokaryotes such as Pseudomonas aeruginosa and Mycobacterium smegmatis have revealed the presence of distinct C-terminal extensions that modulate DNA-binding properties. We report in the present paper that the lysine-rich C-terminal extension of M. smegmatis Ku contacts the core protein domain as evidenced by an increase in DNA-binding affinity and a decrease in thermal stability and intrinsic tryptophan fluorescence upon its deletion. Ku deleted for this C-terminus requires free DNA ends for binding, but translocates to internal DNA sites. In contrast, full-length Ku can directly bind DNA without free ends, suggesting that this property is conferred by its C-terminus. Such binding to internal DNA sites may facilitate recruitment to sites of DNA damage. The results of the present study also suggest that extensions beyond the shared core domain may have independently evolved to expand Ku function.
Skip Nav Destination
Article navigation
December 2013
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
- PDF Icon PDF LinkEditorial Board
Research Article|
November 08 2013
Mycobacterium smegmatis Ku binds DNA without free ends
Ambuj K. Kushwaha;
Ambuj K. Kushwaha
*Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, U.S.A.
Search for other works by this author on:
Anne Grove
Anne Grove
1
*Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, U.S.A.
1To whom correspondence should be addressed (email [email protected]).
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
June 05 2013
Revision Received:
September 16 2013
Accepted:
September 24 2013
Accepted Manuscript online:
September 24 2013
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2013 Biochemical Society
2013
Biochem J (2013) 456 (2): 275–282.
Article history
Received:
June 05 2013
Revision Received:
September 16 2013
Accepted:
September 24 2013
Accepted Manuscript online:
September 24 2013
Citation
Ambuj K. Kushwaha, Anne Grove; Mycobacterium smegmatis Ku binds DNA without free ends. Biochem J 1 December 2013; 456 (2): 275–282. doi: https://doi.org/10.1042/BJ20130749
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.