Fig. 3.

Schematic representation of the typical head-to-tail trimer arrangement of KshA enzymes (adapted from Capyk et al. 2009). Three KshA units are shown in light grey, dark grey and black, forming a circle. Also the FAD co-factor and the iron–sulphur cluster of KshB are depicted. Electrons (e−) are transferred from the iron–sulphur cluster of KshA to the non-heme Fe2+ of the neighbouring KshA unit. AD and 9OHAD indicate 4-androstene-3,17-dione and 9α-hydroxy-4-androstene-3,17-dione, respectively (Petrusma 2011)