Joseph, Nimesh and Sawarkar, Ritwick and Rao, Desirazu N (2004) DNA mismatch correction in Haemophilus inﬂuenzae:characterization of MutL, MutH and their interaction. In: DNA Repair, 3 . pp. 1561-1577.
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Haemophilus inﬂuenzae DNA mismatch repair proteins, MutS, MutL and MutH, are functionally characterized in this study. Introduction of mutS, mutL and mutH genes of H.inﬂuenzae resulted in complementation of the mismatch repair activity of the respective mutant strains of Escherichia coli to varying levels. DNA binding studies using H.inﬂuenzae MutH have shown that the protein is capable of binding to any DNA sequence non-specifically in a co-operative and metal independent manner. Presence of MutL and ATP in the binding reaction resulted in the formation of a more specific complex, which indicates that MutH is conferred specificity for binding hemi-methylated DNA through structural alterations mediated by its interaction with MutL. To study the role of conserved amino acids Ile213 and Leu214 in the helix at the C-terminus of MutH, they were mutated to alanine. The mutant proteins showed considerably reduced DNA binding and nicking, as well as MutL-mediated activation. MutH failed to nick HU bound DNA whereas MboI and Sau3AI, which have the same recognition sequence as MutH, efficiently cleaved the substrate. MutS ATPase activity was found to be reduced two-fold in presence of covalently closed circular duplex containing a mismatched base pair whereas, the activity was regained upon linearization of the circular duplex. This observation possibly suggests that the MutS clamps are trapped in the closed DNA heteroduplex. These studies, therefore, serve as the basis for a detailed investigation of the structure-function relationship among the protein partners of the mismatch repair pathway of H.inﬂuenzae.
|Item Type:||Journal Article|
|Additional Information:||Copyright for this article belongs to Elsevier.|
|Keywords:||Haemophilus inﬂuenzae; DNA mismatch repair; MutH; MutS; MutL; ATPase|
|Department/Centre:||Division of Biological Sciences > Biochemistry|
|Date Deposited:||17 Jan 2006|
|Last Modified:||19 Sep 2010 04:22|
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