Crystal structure of oxidized PcrAB heterodimer reveals [Fe-S] clusters are 10–12 Å apart from the adjacent cluster and the Mo-bis-MGD cofactor.
A, overall crystal structure of oxidized PcrAB. PcrA and PcrB are shown in green and cyan ribbon, respectively. [Fe-S] clusters are shown in sphere (iron, brown; sulfur, yellow), bis-MGD cofactor is shown in magenta ball-and-stick, and molybdenum is shown in turquoise sphere. B, the relative position of cofactors in PcrAB along with Asp170 and a water molecule that coordinate to the active site molybdenum atom. Edge-to-edge distances between cofactors are shown. Labeling of the [Fe-S] clusters is consistent with previous publications (35, 36). The tricyclic pyranopterin of the molybdopterin cofactor is labeled as MGD, and the bicyclic dihydropterin is labeled as MD1. C, electron density 2|Fo| − |Fc| simulated annealing omit maps (gray) at 1.5 σ contour level of PcrA cofactors and active site for oxidized PcrAB. The tricyclic pyranopterin of the molybdopterin cofactor is labeled as MGD, and the bicyclic dihydropterin is labeled as MD1.