Electron transfer flavoprotein from pig liver mitochondria. A simple purification and re-evaluation of some of the molecular properties

Abstract

Electron transfer flavoprotein (ETF) from pig liver mitochondria was purified to homogeneity by a 3-step procedure with .apprx. 10-fold higher yields than previously reported. The purified ETF exhibits an absorption coefficient for the bound FAD of 13.5 mM-1 .cntdot. cm-1 at 436 nm and an isoelectric point of 6.75. Gel filtration, sodium dodecyl sulfate gel electrophoresis and flavin analysis indicate that pig liver ETF is a dimer, composed of non-identical subunits (MW 88,000 and 32,000) with only 1 FAD/dimer. Anaerobic reduction by dithionite produces anionic flavin semiquinone as a stable intermediate and establishes the flavin to be the only redox-active chromophore in ETF.