Transcriptional regulation of the gene encoding lipoyl synthase in Bacillus subtilis

MARTIN, N.; DE-MENDOZA, D.; MARIA CECILIA MANSILLA

Rosario

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

Lipoic acid (1,2-dithiolane-3-pentanoic acid) is a sulfur-containing cofactor essential for function of several key enzymes involved in oxidative metabolism. The biosynthetic pathway of this important cofactor is poorly understood in Bacillus subtilis. It was recently demonstrated in our laboratory that yutB codes a lipoyl synthase in B. subtilis, so the gene was renamed lipA. The aim of the present work was to study the regulation of this gene under different growth conditions. This was accomplished by monitoring the expression of PlipA-lacZ transcriptional fusions and assaying â-galactosidase activity. The results indicate that lipA expression is repressed during growth on poor sulfur sources, such as glutathione and sulphate, and increased in the presence of methionine. We also found out that lipA expression was temperature-dependent: a decrease in growth temperature induces the expression of the gene. In order to determine the involvement of the B. subtilis two component system DesK-DesR and its homologous YvfT-YvfU in the temperature-dependent lipA expression, we analyzed the expression in mutants in ∆desKR, ∆yvfTU and in both systems. We observed that the temperature regulation of lipA expression is not modified in these mutants. In addition, in order to characterize the lipA promoter we are performing primer extension experiments to map the transcription initiation site.