TY - JOUR

T1 - The RES domain toxins of RES-Xre toxin-antitoxin modules induce cell stasis by degrading NAD+

AU - Skjerning, Ragnhild Bager

AU - Senissar, Meriem

AU - Winther, Kristoffer S.

AU - Gerdes, Kenn

AU - Brodersen, Ditlev E.

PY - 2019/1

Y1 - 2019/1

N2 - Type II toxin-antitoxin (TA) modules, which are important cellular regulators in prokaryotes, usually encode two proteins, a toxin that inhibits cell growth and a nontoxic and labile inhibitor (antitoxin) that binds to and neutralizes the toxin. Here, we demonstrate that the res-xre locus from Photorhabdus luminescens and other bacterial species function as bona fide TA modules in Escherichia coli. The 2.2 Å crystal structure of the intact Pseudomonas putida RES-Xre TA complex reveals an unusual 2:4 stoichiometry in which a central RES toxin dimer binds two Xre antitoxin dimers. The antitoxin dimers each expose two helix-turn-helix DNA-binding domains of the Cro repressor type, suggesting the TA complex is capable of binding the upstream promoter sequence on DNA. The toxin core domain shows structural similarity to ADP-ribosylating enzymes such as diphtheria toxin but has an atypical NAD + -binding pocket suggesting an alternative function. We show that activation of the toxin in vivo causes a depletion of intracellular NAD + levels eventually leading to inhibition of cell growth in E. coli and inhibition of global macromolecular biosynthesis. Both structure and activity are unprecedented among bacterial TA systems, suggesting the functional scope of bacterial TA toxins is much wider than previously appreciated.

AB - Type II toxin-antitoxin (TA) modules, which are important cellular regulators in prokaryotes, usually encode two proteins, a toxin that inhibits cell growth and a nontoxic and labile inhibitor (antitoxin) that binds to and neutralizes the toxin. Here, we demonstrate that the res-xre locus from Photorhabdus luminescens and other bacterial species function as bona fide TA modules in Escherichia coli. The 2.2 Å crystal structure of the intact Pseudomonas putida RES-Xre TA complex reveals an unusual 2:4 stoichiometry in which a central RES toxin dimer binds two Xre antitoxin dimers. The antitoxin dimers each expose two helix-turn-helix DNA-binding domains of the Cro repressor type, suggesting the TA complex is capable of binding the upstream promoter sequence on DNA. The toxin core domain shows structural similarity to ADP-ribosylating enzymes such as diphtheria toxin but has an atypical NAD + -binding pocket suggesting an alternative function. We show that activation of the toxin in vivo causes a depletion of intracellular NAD + levels eventually leading to inhibition of cell growth in E. coli and inhibition of global macromolecular biosynthesis. Both structure and activity are unprecedented among bacterial TA systems, suggesting the functional scope of bacterial TA toxins is much wider than previously appreciated.

KW - Bacterial Toxins/chemistry

KW - Crystallography, X-Ray

KW - Escherichia coli/genetics

KW - NAD/metabolism

KW - Photorhabdus/genetics

KW - Protein Conformation

KW - Protein Multimerization

KW - Pseudomonas putida/genetics

KW - Toxin-Antitoxin Systems

UR - http://www.scopus.com/inward/record.url?scp=85056281434&partnerID=8YFLogxK

U2 - 10.1111/mmi.14150

DO - 10.1111/mmi.14150

M3 - Journal article

C2 - 30315706

AN - SCOPUS:85056281434

VL - 111

SP - 221

EP - 236

JO - Molecular Microbiology

JF - Molecular Microbiology

SN - 0950-382X

IS - 1

ER -