This domain family is found in bacteria, and is approximately 110 amino acids in length. The family is found in association with pfam02770, pfam00441, pfam02771. There is a conserved ARRL sequence motif. The C terminal domain is an alpha helical domain. The flavin ring of Acyl-CoA dehydrogenase is buried in the crevice between the two alpha helical domains and the beta-sheet domain of one subunit, and the adenosine pyrophosphate moiety is stretched into the subunit junction of a neighboring subunit, composed of two C terminal domains.