8POP

HK97 small terminase in complex with DNA

Summary for 8POP

• Entry DOI: 10.2210/pdb8pop/pdb
• EMDB information: 17794
• Descriptor: Terminase small subunit, DNA (31-MER) (3 entities in total)
• Functional Keywords: small terminase, hk97, bacteriophage, complex with dna, dna binding protein
• Biological source: Escherichia phage HK97; More
• Total number of polymer chains: 11
• Total formula weight: 185536.21

Authors

Chechik, M.,Greive, S.J.,Antson, A.A.,Jenkins, H.T. (deposition date: 2023-07-05, release date: 2023-08-09, Last modification date: 2024-08-21)

Primary citation

Chechik, M.,Greive, S.J.,Antson, A.A.,Jenkins, H.T.
Structural basis for DNA recognition by a viral genome-packaging machine.
Proc.Natl.Acad.Sci.USA, 121:e2406138121-e2406138121, 2024

PubMed Abstract: DNA recognition is critical for assembly of double-stranded DNA viruses, particularly for the initiation of packaging the viral genome into the capsid. The key component that recognizes viral DNA is the small terminase protein. Despite prior studies, the molecular mechanism for DNA recognition remained elusive. Here, we address this question by identifying the minimal site in the bacteriophage HK97 genome specifically recognized by the small terminase and determining the structure of this complex by cryoEM. The circular small terminase employs an entirely unexpected mechanism in which DNA transits through the central tunnel, and sequence-specific recognition takes place as it emerges. This recognition stems from a substructure formed by the N- and C-terminal segments of two adjacent protomers which are unstructured when DNA is absent. Such interaction ensures continuous engagement of the small terminase with DNA, enabling it to slide along the DNA while simultaneously monitoring its sequence. This mechanism allows locating and instigating packaging initiation and termination precisely at the specific sequence.

PubMed: 39116131
DOI: 10.1073/pnas.2406138121

Experimental method

ELECTRON MICROSCOPY (3 Å)