6fkg
From Proteopedia
Crystal structure of the M.tuberculosis MbcT-MbcA toxin-antitoxin complex.
Structural highlights
FunctionMBCT_MYCTU Toxic component of a type II toxin-antitoxin (TA) system. Neutralized by cognate antitoxin MbcA (PubMed:30315706, PubMed:30792174). Degrades NAD(+) by phosphorolysis. Expression in the absence of its cognate antitoxin MbcA causes dramatic reduction of intracellular NAD(+) levels and is deleterious to cell growth, causing cell death. In a SCID mouse infection model, mice infected with bacteria overexpressing this protein survive longer. Overexpression of this protein in a mouse infection model at 21 days leads to bacterial death, and shows a synergistic 100-fold increase in mouse survival when combined with isoniazid treatment (PubMed:30792174).[1] [2] Publication Abstract from PubMedToxin-antitoxin (TA) systems regulate fundamental cellular processes in bacteria and represent potential therapeutic targets. We report a new RES-Xre TA system in multiple human pathogens, including Mycobacterium tuberculosis. The toxin, MbcT, is bactericidal unless neutralized by its antitoxin MbcA. To investigate the mechanism, we solved the 1.8 A-resolution crystal structure of the MbcTA complex. We found that MbcT resembles secreted NAD(+)-dependent bacterial exotoxins, such as diphtheria toxin. Indeed, MbcT catalyzes NAD(+) degradation in vitro and in vivo. Unexpectedly, the reaction is stimulated by inorganic phosphate, and our data reveal that MbcT is a NAD(+) phosphorylase. In the absence of MbcA, MbcT triggers rapid M. tuberculosis cell death, which reduces mycobacterial survival in macrophages and prolongs the survival of infected mice. Our study expands the molecular activities employed by bacterial TA modules and uncovers a new class of enzymes that could be exploited to treat tuberculosis and other infectious diseases. An NAD(+) Phosphorylase Toxin Triggers Mycobacterium tuberculosis Cell Death.,Freire DM, Gutierrez C, Garza-Garcia A, Grabowska AD, Sala AJ, Ariyachaokun K, Panikova T, Beckham KSH, Colom A, Pogenberg V, Cianci M, Tuukkanen A, Boudehen YM, Peixoto A, Botella L, Svergun DI, Schnappinger D, Schneider TR, Genevaux P, de Carvalho LPS, Wilmanns M, Parret AHA, Neyrolles O Mol Cell. 2019 Feb 18. pii: S1097-2765(19)30048-6. doi:, 10.1016/j.molcel.2019.01.028. PMID:30792174[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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