Binds the promoter region of at least fabA and fabB, but probably not yqfA (PubMed:11160901, PubMed:19854834, PubMed:21276098). Represses the transcription of fabA and fabB, involved in unsaturated fatty acid (UFA) biosynthesis (PubMed:11859088). By controlling UFA production, FabR directly influences the physical properties of the membrane bilayer. Has been suggested to require either an unsaturated acyl carrier protein or unsaturated acyl-CoA (but not their saturated equivalents) for DNA-binding (PubMed:19854834). Another group suggests that unsaturated thioesters are not essential but act instead to enhance DNA-binding (PubMed:21276098). Homodimer. Significantly increased levels of unsaturated fatty acids (UFA) (PubMed:11859088, PubMed:19854834). Double fadR-fabR deletions have increased levels of saturated fatty acids, suggesting a functional fadR gene is required for fabR function (PubMed:11859088). Increased transcription of fabA and fabB (PubMed:11859088, PubMed:21276098). Probably part of the fabR-yijD operon. It is uncertain whether Met-1 or Met-20 is the initiator. Truncated N-terminus.