CRYSTALLIZATION AND PRELIMINARY-X-RAY ANALYSIS OF ELECTRON-TRANSFER FLAVOPROTEINS FROM HUMAN AND PARACOCCUS-DENITRIFICANS

Mammalian electron transfer flavoprotein (ETF) is a soluble, heterodim eric flavoprotein responsible for the oxidation of at least nine prima ry matrix flavoprotein dehydrogenases. Crystals have been obtained for the recombinant human electron transfer flavoprotein (ETF(hum)) by th e sitting-drop vapor diffusion technique using polyethylene glycol (PE G) 1500 at pH 7.0 as the precipitating agent. ETF(hum) crystallizes in the monoclinic space group P2(1), with unit cell parameters a = 47.46 Angstrom, b = 104.10 Angstrom, c = 63.79 Angstrom, and beta = 110.02 degrees. Based on the assumption of one alpha beta dimer per asymmetri c unit, the V-m value is 2.69 Angstrom(3)/Da. A native data set has be en collected to 2.1 Angstrom resolution. One heavy-atom derivative has also been obtained by soaking a preformed crystal of ETF(hum) in 2 mM thimerosal solution for 2 h at 19 degrees C. Patterson analysis indic ates one major site. The analogous electron transfer flavoprotein from Paracoccus denitrificans (ETF(par)) has also been crystallized using PEG 8000 at pH 5.5 as the precipitating agent. ETF(par) crystallizes i n the orthorhombic space group P2(1)2(1)2(1), with unit cell parameter s a = 79.98 Angstrom, b = 182.90 Angstrom, and c = 70.07 Angstrom. The V-m value of 2.33 Angstrom(3)/Da is consistent with two alpha beta di mers per asymmetric unit. A native data set has been collected to 2.5 Angstrom resolution.