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Publication Abstract from PubMed

Bacillus subtilis FadR (FadRBs ), a member of the TetR family of bacterial transcriptional regulators, represses five fad operons including 15 genes, most of which are involved in beta-oxidation of fatty acids. FadRBs binds to the five FadRBs boxes in the promoter regions and the binding is specifically inhibited by long-chain (C14 -C20 ) acyl-CoAs, causing derepression of the fad operons. To elucidate the structural mechanism of this regulator, we have determined the crystal structures of FadRBs proteins prepared with and without stearoyl(C18 )-CoA. The crystal structure without adding any ligand molecules unexpectedly includes one small molecule, probably dodecyl(C12 )-CoA derived from the Escherichia coli host, in its homodimeric structure. Also, we successfully obtained the structure of the ligand-bound form of the FadRBs dimer by co-crystallization, in which two stearoyl-CoA molecules are accommodated, with the binding mode being essentially equivalent to that of dodecyl-CoA. Although the acyl-chain-binding cavity of FadRBs is mainly hydrophobic, a hydrophilic patch encompasses the C1-C10 carbons of the acyl chain. This accounts for the previous report that the DNA binding of FadRBs is specifically inhibited by the long-chain acyl-CoAs but not by the shorter ones. Structural comparison of the ligand-bound and unliganded subunits of FadRBs revealed three regions around residues 21-31, 61-76, and 106-119 that were substantially changed in response to the ligand binding, and particularly with respect to the movements of Leu108 and Arg109. Site-directed mutagenesis of these residues revealed that Arg109, but not Leu108, is a key residue for maintenance of the DNA-binding affinity of FadRBs . Proteins 2014. (c) 2013 Wiley Periodicals, Inc.

Structural characterization of a ligand-bound form of Bacillus subtilis FadR involved in the regulation of fatty acid degradation.,Fujihashi M, Nakatani T, Hirooka K, Matsuoka H, Fujita Y, Miki K Proteins. 2013 Dec 20. doi: 10.1002/prot.24496. PMID:24356978^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.