This family contains sequences that are similar to the fatty acid metabolism regulator protein (FadR, Swiss:P09371). This functions as a dimer, with each monomer being composed of an N-terminal DNA-binding domain and a regulatory C-terminal domain. A linker comprising two short alpha helices joins the two domains. In the C-terminal domain, an antiparallel array of six alpha helices forms a barrel-like structure, while a seventh alpha helix forms a 'lid' at the end closest to the N-terminal domain. This structure was found to be similar to that of the C-terminal domain of the Tet repressor. Long-chain acyl-CoA thioesters interact directly and reversibly with the C-terminal domain, and this interaction affects the structure and therefore the DNA binding properties of the N-terminal domain [1].

1: The FadR.DNA complex. Transcriptional control of fatty acid metabolism in Escherichia coli. Xu Y, Heath RJ, Li Z, Rock CO, White SW; J Biol Chem 2001;276:17373-17379. PMID:11279025