Detailed studies of the binding mechanism of the Sinorhizobium meliloti transcriptional activator ExpG to DNA

Birgit Baumgarth, Frank Wilco Bartels, Dario Anselmetti, Anke Becker, Robert Ros

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

The exopolysaccharide galactoglucan promotes the establishment of symbiosis between the nitrogen-fixing Gram-negative soil bacterium Sinorhizobium meliloti 2011 and its host plant alfalfa. The transcriptional regulator ExpG activates expression of galactoglucan biosynthesis genes by direct binding to the expA1, expGlexpD1 and expE1 promoter regions. ExpG is a member of the MarR family of regulatory proteins. Analysis of target sequences of an ExpG(His)6, fusion protein in the exp promoter regions resulted in the identification of a binding site composed of a conserved palindromic region and two associated sequence motifs. Association and dissociation kinetics of the specific binding of ExpG(His)6 to this binding site were characterized by standard biochemical methods and by single-molecule spectroscopy based on the atomic force microscope (AFM). Dynamic force spectroscopy indicated a distinct difference in the kinetics between the wild-type binding sequence and two mutated binding sites, leading to a closer understanding of the ExpG-DNA interaction.

Original languageEnglish (US)
Pages (from-to)259-268
Number of pages10
JournalMicrobiology
Volume151
Issue number1
DOIs
StatePublished - Jan 2005
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology

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