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Lokareddy RK, Hou CFD, Doll SG, Li F, Gillilan RE, Forti F, Horner DS, Briani F, Cingolani G. Terminase Subunits from the Pseudomonas-Phage E217. J Mol Biol 2022; 434:167799. [PMID: 36007626 PMCID: PMC10026623 DOI: 10.1016/j.jmb.2022.167799] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/17/2022] [Accepted: 08/17/2022] [Indexed: 11/16/2022]
Abstract
Pseudomonas phages are increasingly important biomedicines for phage therapy, but little is known about how these viruses package DNA. This paper explores the terminase subunits from the Myoviridae E217, a Pseudomonas-phage used in an experimental cocktail to eradicate P. aeruginosa in vitro and in animal models. We identified the large (TerL) and small (TerS) terminase subunits in two genes ∼58 kbs away from each other in the E217 genome. TerL presents a classical two-domain architecture, consisting of an N-terminal ATPase and C-terminal nuclease domain arranged into a bean-shaped tertiary structure. A 2.05 Å crystal structure of the C-terminal domain revealed an RNase H-like fold with two magnesium ions in the nuclease active site. Mutations in TerL residues involved in magnesium coordination had a dominant-negative effect on phage growth. However, the two ions identified in the active site were too far from each other to promote two-metal-ion catalysis, suggesting a conformational change is required for nuclease activity. We also determined a 3.38 Å cryo-EM reconstruction of E217 TerS that revealed a ring-like decamer, departing from the most common nonameric quaternary structure observed thus far. E217 TerS contains both N-terminal helix-turn-helix motifs enriched in basic residues and a central channel lined with basic residues large enough to accommodate double-stranded DNA. Overexpression of TerS caused a more than a 4-fold reduction of E217 burst size, suggesting a catalytic amount of the protein is required for packaging. Together, these data expand the molecular repertoire of viral terminase subunits to Pseudomonas-phages used for phage therapy.
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Affiliation(s)
- Ravi K Lokareddy
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
| | - Chun-Feng David Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
| | - Steven G Doll
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
| | - Fenglin Li
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
| | - Richard E Gillilan
- Macromolecular Diffraction Facility, Cornell High Energy Synchrotron Source (MacCHESS), Cornell University, 161 Synchrotron Drive, Ithaca, NY 14853, USA
| | - Francesca Forti
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - David S Horner
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Federica Briani
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy.
| | - Gino Cingolani
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA.
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