Structural characterization of MepB from Staphylococcus aureus reveals homology to endonucleases

Area of Science:

• Microbiology
• Structural Biology
• Molecular Biology

Background:

• The MepRAB operon in Staphylococcus aureus is implicated in antimicrobial resistance.
• While MepA and MepR functions are understood, MepB's role remains largely uncharacterized.

Purpose of the Study:

• To elucidate the structure and potential function of MepB.
• To investigate MepB's interaction with nucleic acids in the context of drug resistance.

Main Methods:

• X-ray crystallography to determine MepB's three-dimensional structure.
• Nucleic acid binding assays to assess MepB's affinity for DNA and RNA.

Main Results:

• The X-ray structure of MepB was resolved to 2.1 Å, showing similarity to PD-(D/E)XK endonucleases.
• MepB demonstrated binding to both DNA and RNA, with preferential affinity for RNA and single-stranded DNA over double-stranded DNA.
• Key catalytic residues typical of the PD-(D/E)XK family were not conserved in MepB.

Conclusions:

• MepB's structural similarity to endonucleases, coupled with its nucleic acid binding capabilities, suggests a role in the MepRAB drug resistance operon.
• Despite lacking conserved catalytic residues, MepB likely contributes to antimicrobial response through nucleic acid interactions.