... unreactive C–H bonds of an octanoyl substrate. This reaction requires lipoyl synthase, a member of the radical S -adenosylmethionine (SAM) enzyme superfamily. In the present study, we solved crystal structures of lipoyl synthase with two [4Fe–4S] clusters bound at opposite ends of the TIM barrel, the usual...

... of the octanoyl chain. The challenging chemistry of this last step is performed by the radical S -adenosylmethionine (SAM) enzyme lipoyl synthase (LipA). In this issue of the Biochemical Journal , Harmer et al. report the first crystal structure of a lipoyl synthase and demonstrate that it contains two [4Fe–4S...