Electron Transfer Flavoprotein Alpha Polypeptide (ETFa)

Electron transfer flavoprotein (ETF) exists in the mitochondrial matrix as a heterodimer of 30-kD alpha subunits (ETFA) and 28-kD beta subunits (ETFB) and contains 1 flavin adenine dinucleotide (FAD) and 1 adenosine 5-prime monophosphate (AMP) per heterodimer. ETFDH, a 64-kD monomer integrated in the inner mitochondrial membrane, contains 1 molecule of FAD and a 4Fe-4S cluster. Both enzymes are required for electron transfer from at least 9 mitochondrial flavin-containing dehydrogenases to the main respiratory chain. Multiple acyl-CoA dehydrogenation deficiency (MADD)can be caused by mutation in any of the 3 ETF genes. The disorders resulting from defects in the ETFA, ETFB, and ETFDH genes are referred to as glutaric aciduria IIA, IIB, and IIC, respectively, although there appears to be no difference in the clinical phenotypes.