Publication Date:
2013-08-09
Description:
The Mga Spn transcriptional regulator contributes to the virulence of Streptococcus pneumoniae . It is thought to be a member of the Mga/AtxA family of global regulators. Mga Spn was shown to activate in vivo the P1623B promoter, which is divergent from the promoter ( Pmga ) of its own gene. This activation required a 70-bp region ( PB activation region) located between both promoters. In this work, we purified an untagged form of the Mga Spn protein, which formed dimers in solution. By gel retardation and footprinting assays, we analysed the binding of Mga Spn to linear double-stranded DNAs. Mga Spn interacted with the PB activation region when it was placed at internal position on the DNA. However, when it was positioned at one DNA end, Mga Spn recognized preferentially the Pmga promoter placed at internal position. In both cases, and on binding to the primary site, Mga Spn spread along the adjacent DNA regions generating multimeric protein–DNA complexes. When both Mga Spn -binding sites were located at internal positions on longer DNAs, electron microscopy experiments demonstrated that the PB activation region was the preferred target. DNA molecules totally or partially covered by Mga Spn were also visualized. Our results suggest that Mga Spn might recognize particular DNA conformations to achieve DNA-binding specificity.
Print ISSN:
0305-1048
Electronic ISSN:
1362-4962
Topics:
Biology
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