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. 2006 Oct 20;189(1):65–75. doi: 10.1128/JB.01478-06

FIG. 8.

FIG. 8.

Proposed model of NTD production in B. subtilis. Glucose transported through glucose-PTS (EIICBA) positively regulates NTD production. This activation mechanism is based on the CcpA-dependent catabolite activation mechanism. Under conditions of high glycolytic activity, fructose-1,6-bisphosphate stimulates the phosphorylation of HPr and Crh at Ser46 by activating HprK, leading to CcpA-dependent catabolite activation (11). CcpA and YmfI proteins appear to be involved, directly or indirectly, in de novo synthesis of a precursor(s) for NTD, rather than in ntdABC promoter regulation. By contrast, ntdABC is repressed by GlcP-dependent glucose uptake. Possibly, a presumptive transcriptional regulator (designated X) linking to GlcP-dependent glucose uptake participates in this regulation. The transcriptional activator NtdR binds directly to NTD and activates the ntdABC promoter (18). NTD transporters (Y and Z), which are required for export or import of NTD, have not yet been identified. Positive effects are represented as arrows (→), while the wavy line represents a regulation of the ntdABC promoter by a presumptive transcriptional regulator, X. The glucose-PTS is comprised of enzyme I (EI), enzyme II (EIICBA), and HPr. G6P, glucose-6-phosphate; FBP, fructose-1,6-bisphosphate.