Induction of levansucrase in Bacillus subtilis: an antitermination mechanism negatively controlled by the phosphotransferase system.

AUTOR(ES)

Crutz, A M

RESUMO

The target of the induction by sucrose of the levansucrase gene is a transcription terminator (sacRt) located upstream from the coding sequence, sacB. The two-gene locus sacX-sacY (formerly sacS) and the ptsI gene were previously shown to be involved in this induction. ptsI encodes enzyme I of the phosphoenolpyruvate-dependent phosphotransferase system. SacX is strongly homologous to sucrose-specific phosphotransferase system-dependent permeases. SacY is a positive regulator of sacB. Here we show that SacY is probably an antiterminator interacting directly with sacRt, since in Escherichia coli the presence of the sacY gene stimulates the expression of a reporter gene fused downstream from sacRt. Missense mutations affecting sacY were sequenced, and the sacB regulation was studied in isogenic strains carrying these mutations or in vitro-generated mutations affecting sacX, sacY, or ptsI. The phenotype of double mutants suggests a model in which SacX might be a sucrose sensor that would be phosphorylated by the phosphotransferase system and, in this state, could inhibit the SacY antiterminator. Exogenous sucrose, or a mutation inactivating the phosphotransferase system, would dephosphorylate SacX and allow antitermination at sacRt.

Documentos Relacionados

• Export of extracellular levansucrase by Bacillus subtilis: inhibition by cerulenin and quinacrine.
• Efflux-mediated multidrug resistance in Bacillus subtilis: similarities and dissimilarities with the mammalian system.
• Regulation of the sacPA operon of Bacillus subtilis: identification of phosphotransferase system components involved in SacT activity.
• Regulation of glycerol uptake by the phosphoenolpyruvate-sugar phosphotransferase system in Bacillus subtilis.
• Elucidation of regulatory elements that control damage induction and competence induction of the Bacillus subtilis SOS system.