Figure 2.

Structures of the molybdenum‐ or tungsten‐containing active sites of various formate‐reducing or CO₂‐oxidizing enzymes. The structures are for E. coli FdhF formate dehydrogenase (PDB 1FDO), the FdnG subunit of the E. coli FdnGHI formate dehydrogenase (PDB 1KQF), the FdhA subunit of the D. gigas FdhAB formate dehydrogenase (PDB 1H0H) and the FwdBD subunits of the M. wolfeii formylmethanofuran dehydrogenase (PDB 5T61). The molybdenum and tungsten centers are represented in stick mode, and the [4Fe‐4S] clusters common to all four proteins in space‐filling mode.