FIG 9.

The Thermosynechococcus elongates LipA structure (106). The auxiliary cluster (Aux) is to the left, and the radical SAM (RS) cluster is to the right. The SAM was modeled in based on the binding of the SAM decomposition product, methylthioadenosine, and the complex of another radical SAM enzyme with SAM, whereas the octanoate moiety was docked into a channel between the SAM molecule and the auxiliary cluster (106). The docking is supported by the demonstration that C-6 of octanoate is sufficiently close to the auxiliary cluster for sulfide extraction to occur (112). (Reprinted from reference 106 with permission.)