The electron transfer flavoprotein serves as a specific electron acceptor for several dehydrogenases, including five acyl-CoA dehydrogenases, glutaryl-CoA and sarcosine dehydrogenase. It transfers the electrons to the main mitochondrial respiratory chain via ETF-ubiquinone oxidoreductase (ETF dehydrogenase) (By similarity). Binds 1 FAD per dimer. Heterodimer of an alpha and a beta subunit. Present with 2950 molecules/cell in log phase SD medium. Belongs to the ETF alpha-subunit/FixB family.