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<p>The Retron system is a crucial prokaryotic anti-phage defense mechanism, composed of a noncoding RNA, reverse transcriptase, and effector proteins, which synthesizes multicopy single-stranded DNA to trigger immune responses. While Retron Ec86’s anti-phage mechanism has been elucidated, other Retron types remain poorly understood. Here, we investigate Retron Ec78, a Type I-A system encoding effector proteins PtuA (ATPase) and PtuB (HNH nuclease). Structural analysis reveals that PtuA hexameric complex putatively bound to PtuB, with ATP playing a key role in hexamer assembly. Beyond its known role in abortive infection via tRNA degradation, we demonstrate that the PtuAB complex also exhibits DNA-cleaving activity. These findings provide novel insights into the assembly and dual functionality of the Retron Ec78 system, advancing our understanding of prokaryotic immune mechanisms against phage infection.</p>

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Structural insights into the assembly and function of Retron Ec78 PtuAB

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年5月9日

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  • Leyuan Duan,
  • Lu Chen,
  • Qian Hu,
  • Xiao Li,
  • Shanshan Li,
  • Kaiming Zhang,
  • Qingguo Gong

摘要

The Retron system is a crucial prokaryotic anti-phage defense mechanism, composed of a noncoding RNA, reverse transcriptase, and effector proteins, which synthesizes multicopy single-stranded DNA to trigger immune responses. While Retron Ec86’s anti-phage mechanism has been elucidated, other Retron types remain poorly understood. Here, we investigate Retron Ec78, a Type I-A system encoding effector proteins PtuA (ATPase) and PtuB (HNH nuclease). Structural analysis reveals that PtuA hexameric complex putatively bound to PtuB, with ATP playing a key role in hexamer assembly. Beyond its known role in abortive infection via tRNA degradation, we demonstrate that the PtuAB complex also exhibits DNA-cleaving activity. These findings provide novel insights into the assembly and dual functionality of the Retron Ec78 system, advancing our understanding of prokaryotic immune mechanisms against phage infection.