| Citation | Type | Method | Main gp9 findings | Key quantitative details | URL / DOI |
|---|---|---|---|---|---|
| Leiman et al., 2000 | Primary | X-ray crystallography; structural analysis | Defines gp9 as a trimeric trigger protein linking long tail fibers (LTFs) to the baseplate; places gp9 in the signaling path LTF → gp9 → gp10 → gp11 → short tail fibers, transmitting receptor-recognition to baseplate rearrangement and DNA ejection (pqac-00000006) | Trimeric gp9; part of sixfold baseplate architecture (pqac-00000006) | https://doi.org/10.1006/jmbi.2000.3989 |
| Leiman et al., 2003 | Review | Structural synthesis of T4 morphogenesis literature | Places gp9 at the wedge vertex of the baseplate, functionally tied to LTF attachment and the baseplate conformational transition that precedes sheath contraction (pqac-00000007) | 31.0 kDa; copy number 18 per virion; wedge-vertex localization (pqac-00000007) | https://doi.org/10.1007/s00018-003-3072-1 |
| Mesyanzhinov et al., 2004 | Review | Structural/biochemical synthesis | Describes gp9 as the structural protein connecting LTFs to the baseplate; permits up/down fiber movement; stabilizes the baseplate against abortive triggering; initiates the transition to the six-pointed star during infection; recombinant gp9 can rescue gp9-defective particles in vitro (pqac-00000003) | 288 aa/monomer; SDS-resistant parallel trimer; atomic structure at 2.3 Å; ~60 × 60 × 130 Å; domains: N-term coiled-coil (1–59), middle (60–164), C-term (175–288) (pqac-00000003) | https://doi.org/10.1007/pl00021751 |
| Rossmann et al., 2004 | Review | Cryo-EM fitting plus crystallographic synthesis | Summarizes gp9 as the LTF attachment site in the wedge region; notes gp9 trimer fits uniquely into the baseplate reconstruction and helps define baseplate organization (pqac-00000005) | ~31.0 kDa; trimer; 18 monomers total, implying six gp9 trimers in the baseplate (pqac-00000005) | https://doi.org/10.1016/j.sbi.2004.02.001 |
| Hu et al., 2015 | Primary | Cryo-electron tomography / 3D reconstruction of infection initiation | Visualizes gp9 in situ at the baseplate-LTF interface; shows sixfold LTF arrangement and supports gp9’s role in connecting fibers to the baseplate during infection initiation; documents the hexagon-to-star baseplate transition after host attachment (pqac-00000008, pqac-00000009) | Sixfold tail fiber symmetry; figure-level evidence labeling gp9 and attached LTF architecture (pqac-00000008, pqac-00000009) | https://doi.org/10.1073/pnas.1501064112 |
| Yap et al., 2016 | Primary | Cryo-EM reconstruction; assembly analysis | Shows gp9 binds domain III of gp7 late in assembly; gp9 and gp11–gp12 stabilize the dome-shaped baseplate; identifies gp9 as a late-added structural stabilizer before infection-triggered rearrangement (pqac-00000002) | gp9 incorporated after wedge assembly; binds gp7 domain III in the assembled baseplate (pqac-00000002) | https://doi.org/10.1073/pnas.1601654113 |
| Arisaka et al., 2016 | Review | Structural/assembly review integrating cryo-EM and crystallography | Summarizes gp9 as the socket for LTFs and direct transmitter of receptor-binding signal into the baseplate; receptor engagement via LTFs triggers dome-to-star conversion, short tail fiber deployment, and sheath contraction (pqac-00000001, pqac-00000004) | 288 aa; stoichiometry listed as 18 copies per particle / trimeric assembly note; associated structures include PDB 1S2E, 5IV5, 5IV7 (pqac-00000001, pqac-00000004) | https://doi.org/10.1007/s12551-016-0230-x |
| Mesyanzhinov et al., 2004 | Review | Structural synthesis | Provides detailed mechanistic model: gp9 C-terminal domain is the collinear LTF attachment site; N-terminal coiled-coil associates with gp7; gp9 can pivot and likely transmits receptor-induced mechanical changes into gp7/gp8, baseplate flattening, and sheath contraction (pqac-00000000) | gp9 density ~180 Å from baseplate axis; pivot up to ~55° about a radial axis (pqac-00000000) | https://doi.org/10.1007/pl00021751 |
| Leprince & Mahillon, 2023 | Review (contextual) | Review of phage adsorption biology | Uses T4 as the best-characterized adsorption/baseplate model; provides modern context for gp9-like baseplate attachment modules in adsorption systems, though not a gp9-focused primary study (pqac-00000008, pqac-00000009) | Contextual only; no new gp9-specific quantitative measurements extracted here (pqac-00000008, pqac-00000009) | https://doi.org/10.3390/v15010196 |
| Zhu et al., 2024 | Review (contextual) | Translational review of T4 biotechnology/vaccine platform | Highlights current real-world use of bacteriophage T4 as an engineering platform; relevant as evidence that deep structural understanding of T4 virion proteins underpins applied T4 design, although gp9 itself is not the main engineering target (pqac-00000008, pqac-00000009) | T4 capsid platform supports dense antigen display; contextual application rather than gp9 quantitation (pqac-00000008, pqac-00000009) | https://doi.org/10.1146/annurev-virology-111821-111145 |


*Table: This table summarizes the key literature supporting functional annotation of bacteriophage T4 baseplate protein gp9 (UniProt P10927). It highlights the strongest evidence for gp9’s role as the long-tail-fiber socket and infection-triggering baseplate component, with quantitative structural details where available.*