IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
A novel mechanism of protein lipoylation in Bacillus subtilis
Autor/es:
NATALIA MARTIN; QUIN CHRISTENSEN; JOHN E. CRONAN JR.; DIEGO DE MENDOZA; MARÍA CECILIA MANSILLA
Lugar:
San Diego, Estados Unidos de América
Reunión:
Congreso; The 15th International Conference on Bacilli; 2009
Resumen:
Lipoic acid (LA), a covalently bound cofactor, is essential for the function of several key enzymes involved in oxidative metabolism. The model for protein lipoylation in E. coli involves two pathways: one in which exogenous LA is transferred to apoproteins in a process mediated by LA ligase (LplA), and an endogenous one, that involves LipB, which transfers octanoate to target proteins. These octanoylated domains are converted into lipoylated derivatives by lipoyl synthase (LipA). In bacteria, enzymes involved in lipoylation have gained increasing attention because of their implication in pathogenicity. B. subtilis has three ORFs that encode products homologous to LplAs: lipJ, lipL and yqhM. Although this bacterium does not contain any ORF with significant similarity with LipB, we have previously demonstrated that in this organism LipL is essential for the endogenous lipoylation pathway, suggesting that this enzyme is responsible for the attachment of octanoic acid to the apoenzymes. We also demonstrated that LipJ has lipoyl transferase activity, which is responsible for protein lipoylation in a lipL mutant during growth with LA. In this work we studied the role of YqhM in protein lipoylation. Since YqhM is homologous to an exogenous ligase, no growth or sporulation defects would be expected in its absence. Surprisingly, an yqhM mutant was impaired to grow in minimal media. Its growth was restored by addition of LA or the products of the lipoylated enzymes. This strain also presented sporulation defects in SM medium, which were partially reverted by the addition of LA. Moreover, in vitro assays of octanoyl transferase activity showed that both LipL and YqhM are required. Due to these results we renamed yqhM as lipM. Notably, in B. subtilis at least three proteins, LipL, LipM and LipA, are essential for the endogenous protein lipoylation pathway, instead of the two-protein model of E. coli.