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Infect. Immun. doi:10.1128/IAI.00658-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Mycobacterium bovis BCG CRP-like protein (CRP_BCG) is a functional DNA binding protein in vitro and in vivo, but its activity differs from that of its M. tuberculosis ortholog Rv3676 (CRP_Mt)

Wadsworth Center, New York State Department of Health, and Department of Biomedical Sciences, School of Public Health, University at Albany, PO Box 22002, Albany, NY 12201-2002

^* To whom correspondence should be addressed. Email: kathleen.mcdonough{at}wadsworth.org.

	Abstract

Mycobacterium tuberculosis Rv3676 encodes a CRP-like protein (CRP_Mt) that has been implicated in global gene regulation, and may play an important role during TB infection. The CRP_Mt ortholog in M. bovis BCG, CRP_BCG, is dysfunctional in an E. coli CRP competition assay, and has been proposed as a potential source of M. bovis BCG's attenuation. We compared CRP_BCG and CRP_Mt in vitro and in vivo, in M. bovis BCG and M. tuberculosis, to evaluate CRP_BCG's potential function in a mycobacterial system. Both proteins formed dimers in mycobacterial lysates, bound to the same target DNA sequences and were similarly affected by the presence of cAMP in DNA binding assays. However, CRP_Mt and CRP_BCG differed in their relative affinities for specific DNA target sequences, and susceptibility to protease digestion. Surprisingly, CRP_BCG DNA binding activity was stronger than that of CRP_Mt both in vitro and in vivo, as measured by electrophoretic mobility shift and chromatin immunoprecipitation assays. Nutrient starvation-associated regulation of several CRP_Mt regulon members also differed between M. bovis BCG and M. tuberculosis. We conclude that CRP_BCG is a functional cAMP-responsive DNA binding protein, with an in vivo DNA binding profile in M. bovis BCG similar to that of CRP_Mt in M. tuberculosis. However, biologically significant functional differences may exist between CRP_BCG and CRP_Mt, with respect to gene regulation, and this issue warrants further study.

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