Crystallographic study of the iron-sulfur flavoprotein trimethylamine dehydrogenase from the bacterium W3A1

Large single crystals of trimethylamine dehydrogenase, containing both [4Fe-4S]²⁺ centers and covalently bound FMN, have been prepared by the macro seeding technique. The crystals are monoclinic, space group P2₁ with cell parameters $\text{a = 147.63}\text{A}\text{?}\text{, b = 71.96}\text{A}\text{?}\text{, c = 83.66}\text{A}\text{?}\text{and}\text{β = 97.64 °}$, and diffract to at least 2.0 Å resolution. There is one dimer of approximately 166,000 M_m per asymmetric unit. A 5.0 Å resolution anomalous scattering difference Patterson has been computed which shows the presence and position of two [4Fe-4S]²⁺ centers in the asymmetric unit. A self-rotation function computed at 6.0 Å resolution indicates a non-crystallographic 2-fold axis relating the two subunits. These results show trimethylamine dehydrogenase to be composed of two identical or very similar subunits each containing one [4Fe-4S]²⁺ center.