Crystallization and preliminary X‐ray analysis of electron transfer flavoproteins from human and paracoccus denitrificans

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Abstract
Mammalian electron transfer flavoprotein (ETF) is a soluble, heterodimeric flavoprotein responsible for the oxidation of at least nine primary matrix flavoprotein dehydrogenases. Crystals have been obtained for the recombinant human electron transfer flavoprotein (ETFhum) by the sitting-drop vapor diffusion technique using polyethylene glycol (PEG) 1500 at pH 7.0 as the precipitating agent. ETFhum crystallizes in the monoclinic space group P21, with unit cell parameters a = 47.46 Å, b = 104.10 Å, c = 63.79 Å, and β = 110.02°. Based on the assumption of one αβ dimer per asymmetric unit, the Vm value is 2.69 Å3/Da. A native data set has been collected to 2.1 Å resolution. One heavy-atom derivative has also been obtained by soaking a preformed crystal of ETFhum in 2 mM thimerosal solution for 2 h at 19 °C. Patterson analysis indicates one major site. The analogous electron transfer flavoprotein from Paracoccus denitrificans (ETFpar) has also been crystallized using PEG 8000 at pH 5.5 as the precipitating agent. ETFpar crystallizes in the orthorhombic space group P212121, with unit cell parameters a = 79.98 Å, b = 182.90 Å, and c = 70.07 Å. The Vm value of 2.33 Å3/Da is consistent with two αβ dimers per asymmetric unit. A native data set has been collected to 2.5 Å resolution.