Structural choreography of bacteriophage N4 ejection proteins and the giant virion-associated RNA polymerase
5 affiliations
- 1Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd, Birmingham, AL, 35294, USA
- 2Department of Microbiology, University of Alabama at Birmingham, 845 19th Street South, Birmingham, AL, 35294, USA
- 3Institutional Research Core Program (IRCP), University of Alabama at Birmingham, 845 19th Street South, Birmingham, AL, 35294, USA
- 4Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
- 5Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd, Birmingham, AL, 35294, USA. [email protected]
Abstract
Schitoviruses are widespread prokaryotic viruses that encapsidate a giant ( ~ 3500-residue) virion-associated RNA polymerase (vRNAP). During infection, vRNAP is expelled into Gram-negative bacteria, along with two additional ejection proteins, to assemble a transient DNA-ejectosome that becomes transcriptionally active, initiating viral replication. Here, we present an integrative structural analysis of the coliphage N4 vRNAP (gp50). We find that this 383 kDa enzyme is a multi-domain, single-chain RNA polymerase, structurally distinct from both compact single-chain RNAPs and large multi-subunit holoenzymes. vRNAP is composed of loosely connected domains and exhibits an intramolecular mode of allosteric regulation through its C-terminal domain. Comparative analysis of intact and genome-released virions identified gp51, which forms an outer-membrane complex, and gp52, which assembles a periplasmic tunnel. These proteins generate heterogeneous pores that facilitate the release of vRNAP. We further uncover a signaling hub in the phage tail, composed of the receptor-binding protein, tail tube, and tail plug, that detects receptor engagement and orchestrates the release of ejection proteins. We propose that the beads-on-a-string architecture of vRNAP enables the translocation of megadalton-scale protein complexes through the ~35 Å channel formed by the tail and ejection proteins. These findings establish N4 as a distinctive model for protein translocation through biological channels.
Related
- A bacteriophage split DNA polymerase incorporates a sliding clamp-derived processivity subunit
- Molecular and Structural Characterisation of the MERS-Coronavirus Polymerase
- DNA polymerase kappa supports repair-associated DNA synthesis and neuronal genome resilience
- Bacteriophage and Antibiotic Resistance Are Positively Associated across a Phylogenetically Diverse Set of Clinical Pseudomonas aeruginosa Isolates
- Function behind choreography: cytoskeletal, nuclear, and mechanical dynamics drive growth transition in root hair development
BibTeX
@article{bellis2026structural,
title = {{Structural choreography of bacteriophage N4 ejection proteins and the giant virion-associated RNA polymerase}},
author = {Nathan F. Bellis and Ravi K. Lokareddy and Mikhail Pavlenok and Ruth Q. Jacobs and Stephanie Cooper Horton and James L. Kizziah and Francesca Forti and David Alan Schneider and Michael Niederweis and Federica Briani and Gino Cingolani},
journal = {Nature Communications},
year = {2026},
month = jun,
doi = {10.1038/s41467-026-74701-w},
url = {https://doi.org/10.1038/s41467-026-74701-w},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Structural choreography of bacteriophage N4 ejection proteins and the giant virion-associated RNA polymerase
AU - Nathan F. Bellis
AU - Ravi K. Lokareddy
AU - Mikhail Pavlenok
AU - Ruth Q. Jacobs
AU - Stephanie Cooper Horton
AU - James L. Kizziah
AU - Francesca Forti
AU - David Alan Schneider
AU - Michael Niederweis
AU - Federica Briani
AU - Gino Cingolani
PY - 2026
DA - 2026/06/18
JO - Nature Communications
DO - 10.1038/s41467-026-74701-w
UR - https://doi.org/10.1038/s41467-026-74701-w
AB - Schitoviruses are widespread prokaryotic viruses that encapsidate a giant ( ~ 3500-residue) virion-associated RNA polymerase (vRNAP). During infection, vRNAP is expelled into Gram-negative bacteria, along with two additional ejection proteins, to assemble a transient DNA-ejectosome that becomes transcriptionally active, initiating viral replication. Here, we present an integrative structural analysis of the coliphage N4 vRNAP (gp50). We find that this 383 kDa enzyme is a multi-domain, single-chain RNA polymerase, structurally distinct from both compact single-chain RNAPs and large multi-subunit holoenzymes. vRNAP is composed of loosely connected domains and exhibits an intramolecular mode of allosteric regulation through its C-terminal domain. Comparative analysis of intact and genome-released virions identified gp51, which forms an outer-membrane complex, and gp52, which assembles a periplasmic tunnel. These proteins generate heterogeneous pores that facilitate the release of vRNAP. We further uncover a signaling hub in the phage tail, composed of the receptor-binding protein, tail tube, and tail plug, that detects receptor engagement and orchestrates the release of ejection proteins. We propose that the beads-on-a-string architecture of vRNAP enables the translocation of megadalton-scale protein complexes through the ~35 Å channel formed by the tail and ejection proteins. These findings establish N4 as a distinctive model for protein translocation through biological channels.
SN - 2041-1723
ER -