FIG 1.

Roles of FadR in V. cholerae. (A) In the absence of LCFAs, FadR represses the expression of genes involved in FA degradation and phospholipid biosynthesis by binding to sites in the promoters of the fadB, fadE, fadH, and plsB genes and activates the expression of genes involved in UFA and SFA biosynthesis by binding to sites in the promoters of the fabA, fabB, fabH, and fabF genes. (B) When exogenous LCFAs are present, they diffuse across the outer membrane through FadL and are activated to LCFA-CoAs by FadD. The resulting activated LCFA-CoAs bind to FadR, causing a conformational change that releases it from DNA and results in derepression and failure to activate its regulated promoters. The mechanism by which it controls virulence is the subject of this work.