FIG. 8.

Model of expression regulation of the gnt genes. In early growth phase, the GntI genes are induced by release of GntR from their operators via binding of gluconate. As cell growth is proceeding (late logarithmic phase), gluconate (GA) may gradually accumulate and is then converted to 5-ketogluconate (5KGA) or idonate (IA) by IdnO and IdnD. The products 5-ketogluconate and idonate bind to GntH, resulting in activation of the GntII genes and repression of the GntI genes. Finally, gluconate depletion inside the cell leads to the repression of the GntI genes by GntR again. The dotted arrow represents the time course of cell growth.