Unique structural features and DNA recognition mechanisms of the PRD-containing virulence regulators MafR and MgaSpn

Area of Science:

• Microbiology
• Structural Biology
• Molecular Biology

Background:

• Phosphotransferase system regulatory domain-containing virulence regulators (PCVRs) are crucial transcription factors in pathogenic bacteria.
• PCVRs regulate virulence gene expression by binding double-stranded DNA (dsDNA) in promoter regions.
• The structural basis for PCVR dsDNA recognition and transcriptional regulation remains largely unknown.

Purpose of the Study:

• To elucidate the unique structure of the Enterococcus faecalis MafR protein.
• To determine the molecular mechanism by which PCVRs recognize and bind dsDNA.
• To investigate the role of N-terminal helix-turn-helix (HTH) domains in PCVR-dsDNA interactions.

Main Methods:

• X-ray crystallography to determine the structure of MafR.
• Biochemical assays to assess dsDNA binding affinity.
• Site-directed mutagenesis to probe the function of HTH domains.
• Molecular modeling to analyze protein-DNA interactions.

Main Results:

• MafR exhibits a unique five-domain architecture with an open-ring conformation, dimerizing into a table-like structure.
• The C-terminal domain mediates dimerization, while two N-terminal HTH domains project from the dimer.
• Tandem HTH domains are essential for dsDNA binding, inserting recognition helices into the major groove.
• This represents a novel DNA recognition mode where two HTH domains cooperate for binding.

Conclusions:

• PCVRs employ a unique structural mechanism for dsDNA binding, utilizing two N-terminal HTH domains simultaneously.
• This dual-HTH domain binding strategy differs from conventional single-HTH domain regulators.
• Findings provide critical structural and molecular insights into bacterial virulence regulation by PCVRs.