Functional characterization of the DNA mismatch binding protein MutS from Haemophilus influenzae

Joseph, Nimesh ; Duppatla, Viswanadham ; Rao, Desirazu N. (2005) Functional characterization of the DNA mismatch binding protein MutS from Haemophilus influenzae Biochemical and Biophysical Research Communications, 334 (3). pp. 891-900. ISSN 0006-291X

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This investigation demonstrates DNA mismatch repair activity in Haemophilus influenzae cell free extracts. The mutS gene as well as purified protein of H. influenzae restored repair activity in complementation assays performed with mutS deficient Escherichia coli strain. The difference in affinity for GT and AC mismatched bases by H. influenzae MutS was reflected in the efficiency with which these DNA heteroduplexes were repaired in vitro, with GT being repaired well and AC the least. Unlike E. coli MutS, the H. influenzae homolog failed to give protein-DNA complex with homoduplex DNA. Interestingly, MutS was found to bind single-stranded DNA but with lesser affinity as compared to heteroduplex DNA. Apart from the nucleotide- and DNA-mediated conformational transitions, as monitored by circular dichroism and limited proteolysis, our data suggest a functional role when H. influenzae MutS encounters single-stranded DNA during exonucleolytic step of DNA repair process. We propose that, conformational changes in H. influenzae MutS not only modulate mismatch recognition but also trigger some of the down stream processes involved in the DNA mismatch repair process.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Haemophilus Influenzae; DNA Mismatch Repair; MutS; ATPase; DNA Binding; Limited Proteolysis; Electrophoretic Mobility Shift; In Vivo Complementation; In Vitro Complementation; Circular Dichroism; Heteroduplex DNA
ID Code:51223
Deposited On:28 Jul 2011 07:26
Last Modified:28 Jul 2011 07:26

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