This is the C-terminal domain secreted by Mycobacterium tuberculosis (Mtb). It induces necrosis of infected cells to evade immune responses. Mtb utilizes the protein CpnT to kill human macrophages by secreting its C-terminal domain (CTD), named tuber ...
This is the C-terminal domain secreted by Mycobacterium tuberculosis (Mtb). It induces necrosis of infected cells to evade immune responses. Mtb utilizes the protein CpnT to kill human macrophages by secreting its C-terminal domain (CTD), named tuberculosis necrotizing toxin (TNT) that induces necrosis. It acts as a NAD+ glycohydrolase which hydrolyzes the essential cellular coenzyme NAD+ in the cytosol of infected macrophages resulting in necrotic cell death [1]. CpnT transports its toxic CTD from the cell surface of M. tuberculosis by proteolytic cleavage, where the toxin is cleaved to induce host cell death [2]. Structural analysis determined that the TNT core contains only six beta-strands as opposed to seven found in all known NAD+-utilizing toxins, and is significantly smaller, with only two short alpha-helices and two 3/10 helices. Furthermore, the putative NAD+ binding pocket identified Q822, Y765 and R757 as residues possibly involved in NAD+-binding and hydrolysis based on similar positions of catalytic amino acids of ADP-ribosylating toxins. While glutamine 822 residue was detected to be highly conserved among TNT homologs [1].
