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<p>ABC toxins are toxin-translocating, pore-forming proteins found in a wide range of insecticidal bacteria and some mammalian pathogens. The <i>Yersinia entomopahaga</i> toxin complex (YenTc) belongs to a distinct subclass of ABC toxins, defined by a divergent molecular architecture. Structural details that define their mechanism of action remain to be elucidated. Here we determine structures of the YenTc holotoxin assembly in both prepore and pore-forming configurations using cryo-EM in conjunction with Alphafold2-assisted structural modelling of flexible domains. We define the structural mechanism via which enzymatically-active chitinase subunits are incorporated, and show using phylogenetic analyses that this subclass-defining feature has evolved relatively recently. Our structures point to the existence of distinct conformational states in YenTc, which may distinguish it from other structurally-characterised ABC toxins, or represent states on a shared mechanistic trajectory. Thus, our findings enhance our understanding of the structural diversity that defines distinct ABC toxin subclasses.</p>

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Complete structures of the YenTc holotoxin prepore and pore reveal the evolutionary basis for chitinase incorporation into ABC toxins

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月15日

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  • Yu Shang Low,
  • Solace G. Roche,
  • Nadezhda A. Aleksandrova,
  • Gabriel Foley,
  • Jason KK Low,
  • Joseph K. Box,
  • Tristan I. Croll,
  • Irene R. Chassagnon,
  • J. Shaun Lott,
  • Evelyne Deplazes,
  • Mikael Bodén,
  • Mark RH Hurst,
  • Sarah J. Piper,
  • Michael J. Landsberg

摘要

ABC toxins are toxin-translocating, pore-forming proteins found in a wide range of insecticidal bacteria and some mammalian pathogens. The Yersinia entomopahaga toxin complex (YenTc) belongs to a distinct subclass of ABC toxins, defined by a divergent molecular architecture. Structural details that define their mechanism of action remain to be elucidated. Here we determine structures of the YenTc holotoxin assembly in both prepore and pore-forming configurations using cryo-EM in conjunction with Alphafold2-assisted structural modelling of flexible domains. We define the structural mechanism via which enzymatically-active chitinase subunits are incorporated, and show using phylogenetic analyses that this subclass-defining feature has evolved relatively recently. Our structures point to the existence of distinct conformational states in YenTc, which may distinguish it from other structurally-characterised ABC toxins, or represent states on a shared mechanistic trajectory. Thus, our findings enhance our understanding of the structural diversity that defines distinct ABC toxin subclasses.