FIG 6.

Model of SmtB-Zur regulation in MSMEG. (A) Under low zinc conditions, the SmtB homodimer binds to the DNA and represses expression of zinc exporter ZitA, whereas Zur detaches from the promoter of zinc importers such as znuABC and allows transcription and thus zinc uptake (red dots). Binding of SmtB to and release of Zur from the DNA also allows graded transcription of smtB-zur. (B) In the presence of zinc, the Zur homodimer binds to the DNA and represses smtB-zur and znuABC expression. In contrast, SmtB detaches from the DNA and zitA transcription is allowed, leading to zinc export.