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. Author manuscript; available in PMC: 2017 Apr 12.
Published in final edited form as: Biochemistry. 2016 Apr 1;55(14):2122–2134. doi: 10.1021/acs.biochem.6b00145

Figure 8.

Figure 8

Proposed mechanisms of thioether crosslink formation in lantipeptides and sactipeptides. (A) Mechanism of thioether crosslink formation in lanthipeptides. Substrate is activated to generate a reactive intermediate (Dha or Dhb), which undergoes Michael addition to generate the initial crosslink. (B) Proposed mechanism for radical-mediated thioether cross-links in sactipeptides. The distinguishing feature of this mechanism relative to those shown in Fig. S5 is formation of a reactive intermediate, such as a ketoimine, analogous to Dha or Dhb in the lantipeptide mechanism, which would be trapped from the re- or si-face to generate mixed regioselective outcomes.