Structure and assembly of bacteriophage T4 head

Area of Science:

• Structural biology
• Molecular biology
• Virology

Background:

• The bacteriophage T4 capsid is a complex structure built from essential proteins gp23*, gp24*, and gp20.
• Understanding phage T4 head assembly and DNA packaging has significantly advanced.
• Non-essential proteins Hoc and Soc reinforce the capsid and are used in display technologies.

Purpose of the Study:

• To elucidate the structural and functional mechanisms of bacteriophage T4 capsid assembly and DNA packaging.
• To investigate the roles of essential and non-essential capsid proteins.
• To understand the dynamics and energetics of the DNA packaging motor.

Main Methods:

• Atomic structure determination (X-ray crystallography, Cryo-EM).
• Structural modeling based on homologous proteins.
• Mutagenesis studies.
• Biophysical techniques (optical tweezers, FRET-FCS).

Main Results:

• Atomic structures of key proteins (gp24, Soc, Ip1*, gp16, gp17) have been determined.
• Phage T4 major capsid protein gp23* shares a fold with other icosahedral phages.
• The T4 DNA packaging motor achieves packaging rates up to 2000 bp/sec.
• DNA translocation is driven by ATP hydrolysis, involving motor state changes and DNA compression.

Conclusions:

• Bacteriophage T4 capsid assembly is a complex process involving protein interactions and chaperone assistance.
• The T4 DNA packaging machine is a highly efficient motor with a unique mechanism for DNA translocation.
• Structural and functional insights advance our understanding of viral assembly and DNA packaging in bacteriophages.