Identification of a Novel Ligase Involved in the

MARTIN, N.; DE MENDOZA, D; MANSILLA, MC

Mar del Plata

Congreso; XLIII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Lipoic acid (LA), a covalently bound cofactor, is essential for functioning of several key enzymes involved in oxidative metabolism. The current model for protein lipoylation involves two pathways: one in which exogenous LA is transfer to apoproteins in a process mediated by LA ligase A (LplA), and an endogenous one, that involves LipB, which transfers octanoic acid to target proteins. These octanoylated domains are converted into lipoylated derivatives by lipoyl synthase. Bacillus subtilis has two ORFs homologous to LplAs (yhfJ and yqhM), but no one significantly similar to LipB. The aim of this work was to identify the enzyme/s involved in the endogenous lipoylation pathway. A candidate was ywfL, a gene whose product is slightly similar to YhfJ. We constructed an ywfL mutant (NM51) which was impaired to grow in minimal media. Its growth was restored by adding acetate, succinate and branched-chain fatty acid precursors, or LA. NM51 sporulates poorly in SM medium, but this was partially reverted by the addition of LA. This strain also showed a strong induction of the transcription of the desaturase gene, suggesting that membrane fluidity can only be increased by raising the amount of unsaturated fatty acids. These results show that YwfL is essential for the endogenous protein lipoylation pathway in B. subtilis, so we renamed ywfL as lipL.