Crystallization and preliminary X-ray crystallographic analysis of the electron-transferring flavoprotein from Megasphaera elsdenii

Electron-transferring flavoprotein from the rumen bacterium Megasphaera elsdenii is a heterodimer (M-r = 75 kDa) containing FAD as cofactor and functioning solely to mediate electron transfer between the prosthetic groups of other proteins. The enzyme was crystallized by the hanging-drop vapour-diffusion method using polyethylene glycol 4000 as precipitant. The crystals obtained belong to the space group P2(1)2(1)2(1) with unit-cell dimensions of a = 58.75, b = 61.77 and c = 122.27 Angstrom. Interestingly the crystals exhibit a low solvent content. Crystals diffracted to beyond 2.5 Angstrom using synchrotron radiation.