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Bacteriophages, or phages, are viruses that specifically infect bacteria, utilizing their genetic material to hijack host cellular machinery for replication. DNA bacteriophages employ single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA) genomes. These phages exhibit diverse replication strategies and host interactions, influencing their ecological roles and applications in biotechnology and medicine.ssDNA BacteriophagesssDNA phages, with their small genomes, utilize unique strategies to...
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Bacteriophages, or phages, are viruses that specifically infect bacteria. Among them, T-even bacteriophages, such as T4, exhibit a well-characterized lytic replication cycle in Escherichia coli (E. coli). This process ensures the rapid proliferation of the virus while ultimately leading to the destruction of the bacterial host.Attachment and DNA InjectionThe infection process begins with the recognition and binding of the T4 phage to the E. coli cell surface. Tail fibers of the phage...
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Bacteriophage T4 Head: Structure, Assembly, and Genome Packaging.

Venigalla B Rao1, Andrei Fokine2, Qianglin Fang3

  • 1Bacteriophage Medical Research Center, Department of Biology, The Catholic University of America, Washington, DC 20064, USA.

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Bacteriophage T4 capsid undergoes significant structural changes during genome packaging. These discoveries reveal dynamic remodeling and high-speed DNA packaging mechanisms in phage biology.

Keywords:
ATPase motorDNA packagingbacteriophage T4head assemblyportal vertex

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Area of Science:

  • Structural biology
  • Molecular biology
  • Virology

Background:

  • Bacteriophage T4 is a model organism for studying biological structures and mechanisms.
  • Recent research has expanded knowledge of T4 capsid structure, portal vertex, and genome packaging.

Purpose of the Study:

  • To elucidate the structural dynamics of the bacteriophage T4 capsid during genome packaging.
  • To understand the mechanisms of structural remodeling and DNA translocation.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) was used to determine the in situ structure of the portal vertex.
  • Single-molecule dynamics were employed to study the packaging motor's mechanism.

Main Results:

  • T4 capsid conformations show dramatic domain movements and a ~70% increase in inner volume.
  • The portal vertex exhibits structural morphing, enabling interactions with capsid proteins and triggering expansion.
  • The packaging motor operates via a continuous burst mechanism, achieving DNA packaging speeds up to 2000 bp/s.

Conclusions:

  • Structural remodeling of the T4 capsid is a dynamic process involving domain movements and protein interactions.
  • The portal vertex plays a crucial role in initiating capsid expansion and coordinating with the packaging motor.
  • The bacteriophage T4 packaging machine demonstrates a highly efficient DNA translocation mechanism.