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| Title | Structure of the giant RNA polymerase ejected from coliphage N4. |
|---|---|
| Journal, issue, pages | Res Sq, Year 2025 |
| Publish date | Oct 21, 2025 |
 Authors | Nathan F Bellis / Ravi K Lokareddy / Mikhail Pavlenok / Stephanie L Cooper Horton / James L Kizziah / Francesca Forti / David A Schneider / Michael Niederweis / Federica Briani / Gino Cingolani /   |
| PubMed Abstract | are widespread prokaryotic viruses that encapsidate a giant (~3,500-residue) virion-associated RNA polymerase (vRNAP). During infection, vRNAP is expelled into Gram-negative bacteria, along with two ... are widespread prokaryotic viruses that encapsidate a giant (~3,500-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. |
 External links | Res Sq / PubMed:41282253 / PubMed Central |
| Methods | EM (single particle) |
| Resolution | 2.61 - 4.3 Å |
| Structure data | EMDB-71768, PDB-9pnq: EMDB-71769, PDB-9pnr: EMDB-71771, PDB-9pnt: EMDB-71773, PDB-9pnv: EMDB-71774, PDB-9pnw: EMDB-72877, PDB-9yf5: EMDB-72880, PDB-9yf8: |
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 Keywords | VIRAL PROTEIN / TRANSFERASE / Single Subunit RNA Polymerase / Bacteriophage Ejection Protein / single-subunit RNAP polymerase / dodecamer / bacteriophage portal |
escherichia phage n4 (virus)