Structural conservation of the myoviridae phage tail sheath protein fold

Area of Science:

• Structural biology
• Microbiology
• Virology

Background:

• Bacteriophage phiKZ is a large virus infecting the human pathogen Pseudomonas aeruginosa.
• Its virion features a large icosahedral head and a long contractile tail.
• Previous studies showed similarities between phiKZ and bacteriophage T4 tail organization.

Purpose of the Study:

• To determine the crystal structure of phiKZ tail sheath proteins.
• To compare the structure and contraction mechanism of phiKZ tail sheath with other bacteriophages, particularly T4.

Main Methods:

• X-ray crystallography was used to determine the structures of phiKZ and prophage tail sheath proteins.
• Cryo-electron microscopy (cryo-EM) was used for reconstructions of the extended tail sheath and polysheath.
• Structural fitting of the phiKZ tail sheath protein into cryo-EM reconstructions.

Main Results:

• Crystal structures of phiKZ and prophage tail sheath proteins were determined at high resolution (1.9–3.3 Å).
• Despite low sequence identity, these proteins exhibit a similar fold.
• Structural analysis revealed that phiKZ tail sheath contraction is similar to that of bacteriophage T4.

Conclusions:

• The tail sheath proteins of bacteriophage phiKZ share structural similarities with those of other myoviruses.
• The mechanism of tail sheath contraction in phiKZ is conserved and analogous to that of bacteriophage T4.
• This study provides insights into the molecular mechanisms of giant phage tail assembly and function.