A rainbow coalition of lipid transcriptional regulators.

Lipids are essential structural constituents of bacterial cell membranes and walls, and their biosynthetic pathways are stringently regulated at both biochemical and genetic levels. The recent surge of new information about transcriptional regulation of bacterial lipid metabolism is highlighted by two studies in this issue of Molecular Microbiology by Hugo Gramajo's research group, who add two transcription factors to the diverse repertoire of lipid biosynthesis regulators. FasR is a Streptomyces coelicolor transcriptional activator of genes in fatty acid synthesis, which supplies substrates for membrane phospholipid and triglyceride storage droplets. MabR is a regulator in Mycobacterium tuberculosis that functions as a repressor of essential genes in the cell wall mycolic acid biosynthetic pathway. MabR also affects the expression of fas, which encodes the multifunctional fatty acid synthase that supports phospholipid and triglyceride synthesis. Despite belonging to the same protein family, the distinct ligand binding domains of FasR and MabR suggest different ligands may regulate their DNA binding. The characterization of FasR/MabR exemplifies the structural and functional diversity of the rainbow coalition of lipid transcriptional regulators that reflects the diverse life styles of bacteria.