Structure-function studies of the staphylococcal methicillin resistance antirepressor MecR2

Area of Science:

• Microbiology
• Structural Biology
• Molecular Biology

Background:

• Methicillin resistance in Staphylococcus aureus is mediated by the mec locus, involving the MecI-MecR1-MecA regulatory axis.
• MecR2 was recently identified as a regulator of methicillin resistance, interacting with the MecI repressor.

Purpose of the Study:

• To elucidate the structural and functional characteristics of the MecR2 protein.
• To understand the role of MecR2 in regulating methicillin resistance in Staphylococcus aureus.

Main Methods:

• Crystal structure determination of MecR2.
• Functional complementation assays using a mecR2 deletion mutant.
• Site-directed mutagenesis and deletion mutant analysis.
• DNA binding assays with double-stranded oligonucleotides.

Main Results:

• The crystal structure of MecR2 revealed distinct N-terminal DNA-binding, intermediate scaffold, and C-terminal dimerization domains.
• MecR2 shares structural similarity with ROK family proteins.
• Mutations affecting putative sugar-binding sites did not impact resistance, while DNA binding was observed.
• Deletions in the DNA-binding and scaffold domains reduced MecR2 activity and methicillin resistance.

Conclusions:

• MecR2 functions as an antirepressor by sequestering and facilitating the degradation of MecI.
• The DNA-binding and scaffold domains of MecR2 are essential for its regulatory function in methicillin resistance.
• These findings provide a structural basis for MecR2's role in Staphylococcus aureus antibiotic resistance.