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Mycobacterium smegmatis RecA Protein is Structurally Similar to but Functionally Distinct from Mycobacterium tuberculosis RecA

Ganesh, N and Muniyappa, K (2003) Mycobacterium smegmatis RecA Protein is Structurally Similar to but Functionally Distinct from Mycobacterium tuberculosis RecA. In: Proteins: Structure, Function, and Bioinformatics, 53 (1). pp. 6-17.

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Abstract

In eubacteria, RecA proteins belong to a large superfamily of evolutionarily conserved, filament-forming, functional homologs of DNA strand exchange proteins. Here, we report the functional characterization of Mycobacterium smegmatis (Ms) and Mycobacterium tuberculosis (Mt) RecA proteins. Although in some respects Ms and Mt RecA proteins are structural and functional homologs of Escherichia coli (Ec) RecA, there are significant differences as well. The single-stranded DNA-binding property of RecA proteins was analyzed by electrophoretic mobility shift assays. We observed that Ms or Mt RecA proteins bound single-stranded DNA in a manner distinct from that of Ec RecA: The former two were able to form protein-DNA complexes in the presence of high salt. Further experiments indicated that Ms or Mt RecA proteins catalyzed adenosine triphosphate hydrolysis at approximately comparable rates across a wide range of pHs. Significantly, DNA strand invasion promoted by Ms or Mt RecA proteins displayed similar kinetics but distinctly different pH profiles. In contrast to MtRecA, MsRecA by itself was unable to form joint molecules across a wide range of pHs. However, regardless of the order in which SSB was added, it was able to stimulate MsRecA to form joint molecules within a narrow pH range, indicating that SSB is a required accessory factor. Together, these results provide a source of sharp contrast between EcRecA and mycobacterial RecAs on the one hand and Mt and Ms RecA proteins on the other.

Item Type: Journal Article
Additional Information: The copyright belongs to WILEY-LISS, INC.
Keywords: reca;ssb;recombination;d loops;joint molecules;mycobacteria
Department/Centre: Division of Biological Sciences > Biochemistry
Date Deposited: 01 Mar 2006
Last Modified: 19 Sep 2010 04:23
URI: http://eprints.iisc.ernet.in/id/eprint/5590

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