A single regulator NrtR controls bacterial NAD+ homeostasis via its acetylation.

Rongsui Gao,Wenhui Wei,Jiaoyu Deng,Jun Li,Bachar H Hassan,Youjun Feng

doi:10.7554/elife.51603

Abstract

Nicotinamide adenine dinucleotide (NAD+) is an indispensable cofactor in all domains of life, and its homeostasis must be regulated tightly. Here we report that a Nudix-related transcriptional factor, designated MsNrtR (MSMEG_3198), controls the de novo pathway of NAD+biosynthesis in M. smegmatis, a non-tuberculosis Mycobacterium. The integrated evidence in vitro and in vivo confirms that MsNrtR is an auto-repressor, which negatively controls the de novo NAD+biosynthetic pathway. Binding of MsNrtR cognate DNA is finely mapped, and can be disrupted by an ADP-ribose intermediate. Unexpectedly, we discover that the acetylation of MsNrtR at Lysine 134 participates in the homeostasis of intra-cellular NAD+ level in M. smegmatis. Furthermore, we demonstrate that NrtR acetylation proceeds via the non-enzymatic acetyl-phosphate (AcP) route rather than by the enzymatic Pat/CobB pathway. In addition, the acetylation also occurs on the paralogs of NrtR in the Gram-positive bacterium Streptococcus and the Gram-negative bacterium Vibrio, suggesting that these proteins have a common mechanism of post-translational modification in the context of NAD+ homeostasis. Together, these findings provide a first paradigm for the recruitment of acetylated NrtR to regulate bacterial central NAD+ metabolism.

Highlights

Nicotinamide adenine dinucleotide (NAD+) is an indispensable cofactor of energy metabolism in all domains of life
Genome context analyses suggested that the genes that encode the enzymes involved in the initial three steps of NAD+ synthesis are organized in a conserved manner as an operon and located adjacent to a Nudix related transcriptional regulator on the chromosome of Mycobacterium species (Figure 1A)
We identified a 23-bp NrtR-binding palindrome conservatively located between the Nudix related transcriptional regulator (nrtR) and nadA/B/C operons in mycobacteria (Figure 1C)

Summary

Introduction

Nicotinamide adenine dinucleotide (NAD+) is an indispensable cofactor of energy metabolism in all domains of life. It acts as an electron carrier in redox reactions (Belenky et al, 2007; Magni et al, 2004), and functions as a co-substrate for a number of non-redox enzymes (DNA ligase [Wilkinson et al, 2001], NAD+-dependent de-acetylase CobB/Sir-2 [Schmidt et al, 2004] and ADP-ribose transferase [Domenighini and Rappuoli, 1996]). The intra-cellular level of NAD+ is dependent on the de novo synthesis pathway and/or its salvage or recycling route (Gazzaniga et al, 2009).

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Conclusion