Structural insight into the distinct regulatory mechanism of the HEPN–MNT toxin-antitoxin system in Legionella pneumophila

• Published in: Nature communications Vol. 15; no. 1; pp. 10188 - 16
• Main Authors: Jin, Chenglong, Jeon, Cha-Hee, Kim, Heung Wan, Kang, Jin Mo, Choi, Yuri, Kang, Sung-Min, Lee, Hyung Ho, Kim, Do-Hee, Han, Byung Woo, Lee, Bong-Jin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24-11-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 631/326/41/1319; 631/45/173; 631/535/1266; 82/103; 82/16; 82/29; 82/58; 82/80; 82/83; Antitoxins; Crystal structure; Humanities and Social Sciences; Legionella pneumophila; Legionnaires' disease bacterium; Modules; multidisciplinary; Regulatory mechanisms (biology); Residues; Science; Science (multidisciplinary); Structural analysis; Structure-function relationships; Toxicity; Toxins; Toxins and antitoxins
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-54551-0

HEPN–MNT, a type VII TA module, comprises the HEPN toxin and the MNT antitoxin, which acts as a nucleotidyltransferase that transfers the NMP moiety to the corresponding HEPN toxin, thereby interfering with its toxicity. Here, we report crystal structures of the
Legionella pneumophila
HEPN–MNT module, including HEPN, AMPylated HEPN, MNT, and the HEPN–MNT complex. Our structural analysis and biochemical assays, suggest that HEPN is a metal-dependent RNase and identify its active site residues. We also elucidate the oligomeric state of HEPN in solution. Interestingly,
L. pneumophila
MNT, which lacks a long C-terminal α4 helix, controls the toxicity of HEPN toxin via a distinct binding mode with HEPN. Finally, we propose a comprehensive regulatory mechanism of the
L. pneumophila
HEPN–MNT module based on structural and functional studies. These results provide insight into the type VII HEPN–MNT TA system.
HEPN–MNT is a bacterial type VII toxin-antitoxin (TA) system, comprising the HEPN toxin and the MNT antitoxin. Crystal structures and functional assays of the HEPN–MNT module suggest that HEPN is a metal-dependent RNase and identify its active site residues and regulatory mechanism.