The Bacillus subtilis yutb gene encodes a lipoate synthetase

LOMBARDÍA, E; MANSILLA, MC; DE MENDOZA, D

Iguazú, Argentina

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2004

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Iso- and anteiso-branched-chain fatty acids are the major components of Bacillus subtilis phospholipids, being essential to maintain the appropriate fluidity of the membrane. The enzyme responsible for the formation of the primers for the synthesis of these fatty acids is the branched-chain á-ketoacid dehydrogenase complex, which requires lipoic acid as coenzyme. Genome sequencing revealed that a B. subtilis gene, yutB, presents high homology with E. coli lipA, whose gene product has been genetically linked to the lipoic acid biosynthesis. We constructed a conditional yutB mutant, under the control of the xylose promoter, EL104. This strain displayed growth defects in minimal media, but growth was restored with addition of xylose, lipoic acid, or branched-chain fatty acid precursors. As determined by gas cromatography, EL104 presents increased levels of straight-chain fatty acids with the concomitant reduction of branched-chain fatty acids. Moreover, this mutant presents twice as much unsaturated fatty acids than the wild type, result coincident with the observed strong induction of the transcription of the desaturase gene. Moreover, a plasmid expressing yutB in the E. coli lipA mutant KER296 complemented its lipoic acid auxotrophy. These results suggest that yutB is responsible for the lipoic acid synthesis in B. subtilis.