Interaction of FapR, a global lipid biosynthesis regulator, with its operator sequences

GEORGINA REH; ALBANESI, D; SCHAEFFER, F; GUSTAVO E. SCHUJMAN; ALZARI, P; DIEGO DE MENDOZA

Carloz Paz

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigadores en Bioquímica (SAIB); 2008

Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular (SAIB)

FapR is a transcriptional regulator that negatively controls the expression of several genes of fatty acid and phospholipid biosynthesis in Bacillus subtilis (the fap regulon). It is the first global regulator of lipid synthesis discovered in bacteria and is largely conserved in Gram positive organisms, including several human pathogens. Malonyl-CoA acts as a negative effector of FapR promoting its release from DNA and the concomitant induction of the regulated promoters. A 17 pb consensus palindromic sequence is located in, or close to, the core promoter elements of all the transcriptional units that are members of the fap regulon. Upon binding, FapR protects approximately a 40 bp DNA region, which includes the palindromic sequence. Physiological and biochemical evidence indicate that in B. subtilis the 6 operons of the fap regulon are regulated by FapR to different extent. In order to understand how FapR differentially regulates the expression of these genes we decided to characterize in detail the FapR-DNA interaction through biochemical and structural approaches. Band shift assays, hydroxyl radical footprinting and isothermal titration calorimetry experiments indicate that FapR binds to DNA as a dimer and that two dimers of FapR bind to the protected sequence contacting the same side of the DNA double-strand.