Structural basis of DNA packaging by a ring-type ATPase from an archetypal viral system

Area of Science:

• Biochemistry
• Structural Biology
• Virology

Background:

• Ring-type NTPases are crucial for essential cellular processes, including viral DNA packaging.
• Double-stranded DNA viruses utilize homomeric ring ATPases for translocating genomic DNA into procapsids.
• Mechanistic understanding of viral DNA packaging is established for pac and phi29 bacteriophage systems, but not for the cos system.

Purpose of the Study:

• To reconstitute and biochemically characterize the cos DNA packaging system from bacteriophage HK97.
• To elucidate the structural basis of DNA translocation in the cos system.
• To investigate the regulatory mechanisms governing ATPase activity in viral DNA packaging.

Main Methods:

• Single-molecule assays utilizing photobleaching to determine ATPase stoichiometry.
• X-ray crystallography to determine the structures of large and small terminase components.
• Mutational and biochemical analyses to probe ATPase multimerization and coordination.

Main Results:

• Successful in vitro reconstitution of the HK97 cos packaging system.
• Crystal structures reveal mechanistic similarities between cos and pac systems.
• Identification of a novel regulatory mechanism for ATPase multimerization and coordination in the HK97 system.

Conclusions:

• The study provides a detailed biochemical and structural description of the HK97 cos DNA packaging system.
• Established mechanistic similarities between cos and pac systems, advancing understanding of viral DNA packaging.
• Laid the groundwork for studying evolutionary relationships among ATP-dependent DNA translocation machineries in double-stranded DNA viruses.