Three-dimensional structure of the iron-sulfur flavoprotein trimethylamine dehydrogenase at 2.4-A resolution

The three-dimensional structure of trimethylamine dehydrogenase from the methylotrophic bacterium W3A1 has been determined to 2.4-A resolution. The enzyme is composed of two identical 83,000-dalton subunits, each of which is folded into three structural domains. The largest domain, at the NH2 terminus of the molecule, is folded as an eight-stranded parallel alpha/beta barrel. It contains the [4Fe-4S] and covalently bound FMN cofactors separated by about 4 A. The folding topology of the large domain and orientation of the FMN cofactor are very similar to those found in glycolate oxidase. The other two domains contain alpha/beta parallel beta sheet topologies with similar folding patterns. The topologies and spatial arrangements of these two domains are remarkably similar to the FAD- and NADPH-binding domains of glutathione reductase.