The pneumococcal MgaSpn virulence transcriptional regulator generates multimeric complexes on linear double-stranded DNA

The MgaSpn transcriptional regulator contributes to the virulence of Streptococcus pneumoniae. It is thought to be a member of the Mga/AtxA family of global regulators. MgaSpn was shown to activate in vivo the P1623B promoter, which is divergent from the promoter (Pmga) of its own gene. This activat...

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Bibliographic Details
Published in:Nucleic acids research 2013-08, Vol.41 (14), p.6975-6991
Main Authors: Solano-Collado, Virtu, Lurz, Rudi, Espinosa, Manuel, Bravo, Alicia
Format: Article
Language:English
Subjects:
Bacterial Proteins - chemistry
Bacterial Proteins - metabolism
Binding Sites
DNA, Bacterial - chemistry
DNA, Bacterial - metabolism
Molecular Biology
Nucleic Acid Conformation
Promoter Regions, Genetic
Protein Binding
Protein Multimerization
Streptococcus pneumoniae
Streptococcus pneumoniae - genetics
Streptococcus pneumoniae - pathogenicity
Trans-Activators - chemistry
Trans-Activators - metabolism
Virulence Factors - chemistry
Virulence Factors - metabolism
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Summary:The MgaSpn transcriptional regulator contributes to the virulence of Streptococcus pneumoniae. It is thought to be a member of the Mga/AtxA family of global regulators. MgaSpn 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 MgaSpn protein, which formed dimers in solution. By gel retardation and footprinting assays, we analysed the binding of MgaSpn to linear double-stranded DNAs. MgaSpn 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, MgaSpn recognized preferentially the Pmga promoter placed at internal position. In both cases, and on binding to the primary site, MgaSpn spread along the adjacent DNA regions generating multimeric protein-DNA complexes. When both MgaSpn-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 MgaSpn were also visualized. Our results suggest that MgaSpn might recognize particular DNA conformations to achieve DNA-binding specificity.
ISSN:0305-1048
1362-4962
DOI:10.1093/nar/gkt445