Synergy between the N-terminal and C-terminal domains of Mycobacterium tuberculosis HupB is essential for high-affinity binding, DNA supercoiling and inhibition of RecA-promoted strand exchange

Sharadamma, N and Khan, Krishnendu and Kumar, Sandeep and Patil, Neelakanteshwar K and Hasnain, Seyed E and Muniyappa, K (2011) Synergy between the N-terminal and C-terminal domains of Mycobacterium tuberculosis HupB is essential for high-affinity binding, DNA supercoiling and inhibition of RecA-promoted strand exchange. In: FEBS Journal, 278 (18). pp. 3447-3462.

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Abstract

The occurrence of DNA architectural proteins containing two functional domains derived from two different architectural proteins is an interesting emerging research theme in the field of nucleoid structure and function. Mycobacterium tuberculosis HupB, unlike Escherichia coli HU, is a two-domain protein that, in the N-terminal region, shows broad sequence homology with bacterial HU. The long C-terminal extension, on the other hand, contains seven PAKK/KAAK motifs, which are characteristic of the histone H1/H5 family of proteins. In this article, we describe several aspects of HupB function, in comparison with its truncated derivatives lacking either the C-terminus or N-terminus. We found that HupB binds a variety of DNA repair and replication intermediates with K(d) values in the nanomolar range. By contrast, the N-terminal fragment of M. tuberculosis HupB (HupB(MtbN)) showed diminished DNA-binding activity, with K(d) values in the micromolar range, and the C-terminal domain was completely devoid of DNA-binding activity. Unlike HupB(MtbN), HupB was able to constrain DNA in negative supercoils and introduce negative superhelical turns into relaxed DNA. Similarly, HupB exerted a robust inhibitory effect on DNA strand exchange promoted by cognate and noncognate RecA proteins, whereas HupB(MtbN), even at a 50-fold molar excess, had no inhibitory effect. Considered together, these results suggest that synergy between the N-terminal and C-terminal domains of HupB is essential for its DNA-binding ability, and to modulate the topological features of DNA, which has implications for processes such as DNA compaction, gene regulation, homologous recombination, and DNA repair.

Item Type:	Journal Article
Publication:	FEBS Journal
Publisher:	John Wiley & Sons
Additional Information:	Copyright of this article belongs to John Wiley & Sons.
Keywords:	DNA strand exchange;DNA supercoiling;HU protein;HupB protein; nucleoid
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	28 Sep 2011 11:17
Last Modified:	28 Sep 2011 11:17
URI:	http://eprints.iisc.ac.in/id/eprint/40769

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