Functional characterization and mechanism of the multidrug resistance transport potein YoeA in Bacillus subtilis.

Transport proteins are essential for bacterial resistance to antibiotics and toxins, but their mechanisms remain poorly understood in Bacillus subtilis. In the present study, overexpression of yoeA enhanced resistance to various antibiotics, with its expression induced by these antibiotics, especially penicillin and plipastatin. The ΔyoeA strain exhibited significant growth inhibition at 100 μg/mL of plipastatin, while as high as 10,000 μg/mL of iturin/surfactin are required to achieve comparable inhibition, suggesting a higher sensitivity of ΔyoeA to plipastatin. The transcript level of yoeA gene was increased 2.71-fold in response to plipastatin, significantly higher than the levels induced by surfactin and iturin. The ethidium bromide (EtBr) efflux activity of YoeA was inhibited by carbonyl cyanide chlorophenylhydrazone (CCCP) and enhanced by Na+. Molecular modeling studies revealed that cation-π interactions of Na+ with Y287 and Y434 residues in the C-terminal domain of YoeA contribute to its ion channel function, and Cu2+ can form coordination bonds with the N atoms of H278 and H421 residues on the C-terminal surface of YoeA, promoting plipastatin efflux in a dose-dependent manner. The present study characterized the main factors influencing YoeA's efflux activity, revealed its transport mechanism, and provided new insights into enhancing antimicrobial peptide production and controlling bacterial resistance.