FIGURE 1.

Electron transfer relay architecture and predicted DmsA structure around FS0. A, predicted electron transfer relay in DmsABC connecting a menaquinol-binding site in the DmsC subunit with the Mo-bisPGD cofactor in the DmsA subunit. In this model, note that DmsC is predicted to be membrane-intrinsic and anchors to DmsA and DmsB to the periplasmic side of the E. coli cytoplasmic membrane (2). B, a structural model of DmsA was generated using the ESyPred3D server (29) with the structure of the NarG subunit of NarGHI as a template (Protein Data Bank code 1Q16) (40). The predicted position of the ¹⁸CTVNC²² loop is shown. The distances shown are arbitrary but indicate a possible H-bonding interaction between Asn-21 and one dithiolene sulfur from each pterin. C, the predicted position of Arg-61 between FS0 and the proximal pterin (PPT-P).