Figure 6.

Schematic diagram of the nisin A highly resistant mechanism. I. A point mutation in the promoter region results in the higher expression of braXRS. This leads to the increased induction of vraDE expression by nisin A. II. A point mutation in braS (encoding a sensor protein) causes nisin A-independent phosphorylation of BraS, resulting in increased phosphorylated BraR, which induces a constant expression of vraDE. III. A point mutation in braR (encoding a response regulator) results in nisin A-independent activation of vraDE expression. IV. A point mutation in pmtR encoding a negative regulator PmtR for pmtABCD expression. Mutated PmtR, which lacks the DNA binding ability, results in a constant pmtABCD expression.