Part of the ETF-acryloyl-CoA reductase complex involved in the pathway of L-alanine fermentation. The electron transfer flavoprotein (ETF) serves as a specific electron acceptor for acryloyl-CoA reductase. Heterohexadecamer; tetramer of tetramers. Each tetramer is composed of 2 alpha (AcrC), a beta (AcrA) and a gamma (AcrB) subunit. Belongs to the ETF beta-subunit/FixA family.