UMass Chan Medical School Faculty Publications

UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology

Publication Date


Document Type

Article Preprint


Amino Acids, Peptides, and Proteins | Bacteria | Biochemistry | Genetic Phenomena | Investigative Techniques | Structural Biology


Tailed bacteriophage use a DNA packaging motor to encapsulate their genome during viral particle assembly. The small terminase (TerS) component acts as a molecular matchmaker by recognizing the viral genome as well as the main motor component, the large terminase (TerL). How TerS binds DNA and the TerL protein remains unclear. Here, we identify the TerS protein of the thermophilic bacteriophage P74-26. TerSP76-26 oligomerizes into a nonamer that binds DNA, stimulates TerL ATPase activity, and inhibits TerL nuclease activity. Our cryo-EM structure shows that TerSP76-26 forms a ring with a wide central pore and radially arrayed helix-turn-helix (HTH) domains. These HTH domains, which are thought to bind DNA by wrapping the helix around the ring, are rigidly held in an orientation distinct from that seen in other TerS proteins. This rigid arrangement of the putative DNA binding domain imposes strong constraints on how TerSP76-26 can bind DNA. Finally, the TerSP76-26 structure lacks the conserved C-terminal β-barrel domain used by other TerS proteins for binding TerL, suggesting that a well-ordered C-terminal β-barrel domain is not necessary for TerS to carry out its function as a matchmaker.


Biochemistry, Tailed bacteriophage, DNA packaging motor, thermophilic phage, proteins, terminase, thermophile, genome packaging, helix-turn-helix, phage, motor

Rights and Permissions

The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It is made available under a CC-BY-ND 4.0 International license.

DOI of Published Version



bioRxiv 851345; doi: Link to preprint on bioRxiv service.

Journal/Book/Conference Title


Creative Commons License

Creative Commons Attribution-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-No Derivative Works 4.0 License.