Figure 2

Homology model of formyl-methanofuran dehydrogenase enzyme (Fwd). The structures of Fwd subunits B and D from M. jannashii were modeled using structural templates from E.coli and A. fulgidus. (a) FwdB consists of three domains. Two of them have Rossmann-like α/β/α folds (green and cyan). The B and D subunits together bind two molecules of molybdenum cofactor dinucleotide MGD [1, 2] shown in sticks representation. The third domain binds a [4Fe-4S] cluster (blue). The subunit D with a β-barrel fold (orange) is also involved in (di)MGD cofactor binding. (b) Surface representation of FwdBD protein complex model with the individual domains colored as in chart a, rotated 180 degrees around the y-axis. (c) Structures of the elementary functional loops (left-to-right): MGD cofactor binding EFL (cyan) from one of the Rossmann-like domains is shown together with one MGD molecule; iron-sulfur cluster-binding EFL (blue) from the ferredoxin-like fold together with the [4Fe-4S] cluster; two psi-loops (orange) constituting the core of the double-psi β-barrel fold are also involved in MGD binding.