A single-amino-acid substitution in the C terminus of PhoP determines DNA-binding specificity of the virulence-associated response regulator from Mycobacterium tuberculosis.

Das, Arijit Kumar and Pathak, Anuj and Sinha, Akesh and Datt, Manish and Singh, Balvinder and Karthikeyan, Subramanian and Sarkar, Dibyendu (2010) A single-amino-acid substitution in the C terminus of PhoP determines DNA-binding specificity of the virulence-associated response regulator from Mycobacterium tuberculosis. Journal of molecular biology, 398 (5). pp. 647-56. ISSN 1089-8638

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Abstract

The Mycobacterium tuberculosis PhoP-PhoR two-component system is essential for virulence in animal models of tuberculosis. Genetic and biochemical studies indicate that PhoP regulates the expression of more than 110 genes in M. tuberculosis. The C-terminal effector domain of PhoP exhibits a winged helix-turn-helix motif with the molecular surfaces around the recognition helix (alpha 8) displaying strong positive electrostatic potential, suggesting its role in DNA binding and nucleotide sequence recognition. Here, the relative importance of interfacial alpha 8-DNA contacts has been tested through rational mutagenesis coupled with in vitro binding-affinity studies. Most PhoP mutants, each with a potential DNA contacting residue replaced with Ala, had significantly reduced DNA binding affinity. However, substitution of nonconserved Glu215 had a major effect on the specificity of recognition. Although lack of specificity does not necessarily correlate with gross change in the overall DNA binding properties of PhoP, structural superposition of the PhoP C-domain on the Escherichia coli PhoB C-domain-DNA complex suggests a base-specific interaction between Glu215 of PhoP and the ninth base of the DR1 repeat motif. Biochemical experiments corroborate these results, showing that DNA recognition specificity can be altered by as little as a single residue change of the protein or a single base change of the DNA. The results have implications for the mechanism of sequence-specific DNA binding by PhoP.

Item Type:	Article
Additional Information:	Copyright of this article belongs to Elsevier Science.
Uncontrolled Keywords:	direct repeats; DNA recognition specificity; M. tuberculosis PhoP; recognition helix; response regulator
Subjects:	Q Science > QR Microbiology
Depositing User:	Dr. K.P.S.Sengar
Date Deposited:	28 Feb 2012 16:08
Last Modified:	28 Feb 2012 16:08
URI:	http://crdd.osdd.net/open/id/eprint/1114

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