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. 2019 Oct 9;8:e51603. doi: 10.7554/eLife.51603

Figure 1. Working model for the regulation of NAD homeostasis by NrtR in Mycobacterium.

Figure 1.

(A) The genetic context of nrtR and its signature in Mycobacterium compared with the NrtR-binding sequences in Streptococcus (B) and Mycobacterium (C). (D) NrtR acts as an auto-repressor and represses the transcription of the nadA-nadB-nadC operon that is responsible for the de novo synthesis of the NAD+ cofactor in Mycobacterium. (E) NAD+ homeostasis proceeds through cooperation of a salvage pathway with de novo synthesis in Mycobacterium. Designations: nadA, the gene encoding quinolinate synthase; nadB, gene encoding L-aspartate oxidase; nadC, gene encoding quinolinate phosphoribosyltransferase; PncA, nicotinamide deaminase; PncB, nicotinate phosphoribosyltransferase; NrtR, a bifunctional transcriptional factor involved in the regulation of NAD+ synthesis; ADP-R, ADP-ribose; Na, nicotinic acid; Nm, nicotinamide; Rib-P, ribose-5-phosphate; Asp, aspartate; NaMN, nicotinate mononucleotide; NAD+, nicotinamide adenine dinucleotide; CobB, an NAD+-consuming deacetylase.