Heterodimeric electron transfer flavoprotein that accepts electrons from several mitochondrial dehydrogenases, including acyl-CoA dehydrogenases, glutaryl-CoA and sarcosine dehydrogenase (PubMed:27499296, PubMed:15159392, PubMed:15975918, PubMed:9334218, PubMed:10356313). It transfers the electrons to the main mitochondrial respiratory chain via ETF-ubiquinone oxidoreductase (ETF dehydrogenase) (PubMed:9334218). Required for normal mitochondrial fatty acid oxidation and normal amino acid metabolism (PubMed:12815589, PubMed:1882842, PubMed:1430199). Binds 1 FAD per dimer. Heterodimer composed of ETFA and ETFB (PubMed:8962055, PubMed:15159392, PubMed:15975918, PubMed:9334218). Identified in a complex that contains ETFA, ETFB and ETFRF1 (PubMed:27499296). Interaction with ETFRF1 promotes dissociation of the bound FAD and loss of electron transfer activity (PubMed:27499296). Interacts with TASOR (By similarity). Domain I shares an identical polypeptide fold with the beta subunit ETFB though there is no sequence similarity. The N-terminus is blocked. The disease is caused by variants affecting the gene represented in this entry. Belongs to the ETF alpha-subunit/FixB family.