Scheme 2.

Two Possible Mechanisms for Formation of the [3Fe-4S]⁰-Like Auxiliary Cluster in MiaB by Nucleophilic Attack of Either a Terminal Sulfide on the Unique Fe Site (A) or a μ₃-Bridging Sulfide (B) from the [4Fe-4S]²⁺ Cluster on the Methyl Group of SAM and the Mechanism for Generation of the [3Fe-4S]⁰-Like Cluster by a Radical Mechanism in LipA (C)^a

^aThe sulfur atom and the methyl group forming the methylthio moiety of the intermediate are emphasized in bold red.