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<p>The post-genome packaging mechanisms that govern the assembly of an infectious virion are poorly understood in bacteriophages and other&#xa0;viruses. Here, our near-atomic resolution cryo-EM structural analyses uncovered an assembly- and conformation-driven genome positioning mechanism in the tailed bacteriophage T4. We show that following headful packaging, which generates a pressurized head, a global conformational change occurs in the portal structure, probably triggering packaging termination and ejection of the packaging motor. Our high-resolution structures of the neck of the virion further show that the neck undergoes conformational changes upon docking of a pre-assembled tail onto the sealed neck, which then opens a genome-gate. Driven by the pressure of the packaged DNA, the genome travels through open neck channels, binds and compresses the resident tape-measure protein, and halts at the bottom of the second topmost disk of the tail tube. Pressure-suspended within the virion’s innermost tunnel and secured by a baseplate plug, the genome remains poised to flow through the tunnel into a host cell upon receiving the host receptor recognition signal.</p>

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In situ structures of the portal-neck-tail complex of bacteriophage T4 inform a viral genome positioning mechanism

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月20日

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  • Andrei Fokine,
  • Jingen Zhu,
  • Thomas Klose,
  • Frank Vago,
  • Charles-Adrien Arnaud,
  • Zhiqing Wang,
  • Baldeep Khare,
  • Michael G. Rossmann,
  • Zhenguo Chen,
  • Lei Sun,
  • Qianglin Fang,
  • Richard J. Kuhn,
  • Venigalla B. Rao

摘要

The post-genome packaging mechanisms that govern the assembly of an infectious virion are poorly understood in bacteriophages and other viruses. Here, our near-atomic resolution cryo-EM structural analyses uncovered an assembly- and conformation-driven genome positioning mechanism in the tailed bacteriophage T4. We show that following headful packaging, which generates a pressurized head, a global conformational change occurs in the portal structure, probably triggering packaging termination and ejection of the packaging motor. Our high-resolution structures of the neck of the virion further show that the neck undergoes conformational changes upon docking of a pre-assembled tail onto the sealed neck, which then opens a genome-gate. Driven by the pressure of the packaged DNA, the genome travels through open neck channels, binds and compresses the resident tape-measure protein, and halts at the bottom of the second topmost disk of the tail tube. Pressure-suspended within the virion’s innermost tunnel and secured by a baseplate plug, the genome remains poised to flow through the tunnel into a host cell upon receiving the host receptor recognition signal.