| Claim/Topic | What is known (concise) | Evidence type | Key quantitative data | Key citation(s) with publication year and URL |
|---|---|---|---|---|
| Identity / size / stoichiometry | T4 gene 36 encodes long-tail fiber protein gp36, a trimeric component of the long tail fiber (LTF); it is not the receptor-binding tip itself but part of the distal rod / hinge-proximal region. | Review synthesis of genetics, EM, structural biology | 221 aa per monomer; ~23.0 kDa; 3 copies per fiber; 6 fibers per virion, implying 18 gp36 copies per virion. | Leiman et al. 2003, *Cell. Mol. Life Sci.* (Nov 2003), https://doi.org/10.1007/s00018-003-3072-1 (pqac-00000000, pqac-00000005); Leiman et al. 2010, *Virology Journal* (Dec 2010), https://doi.org/10.1186/1743-422x-7-355 (pqac-00000001, pqac-00000006) |
| Virion localization | gp36 sits at the proximal end of the distal half-fiber, forming the upper part of the “shin”; it lies between the gp35 kneecap/hinge and the gp37 distal receptor-recognition region. | Cryo-EM-informed review; assembly diagrams; morphogenesis review | Located in distal half-fiber; upper part of “shin”; distal/hinge connection. | Leiman et al. 2010, *Virology Journal* (Dec 2010), https://doi.org/10.1186/1743-422x-7-355 (pqac-00000001, pqac-00000012); Leiman et al. 2003, *Cell. Mol. Life Sci.* (Nov 2003), https://doi.org/10.1007/s00018-003-3072-1 (pqac-00000000, pqac-00000005) |
| Assembly interactions | Distal half-fiber assembly proceeds by gp36 trimer binding the N-terminus of gp37; then a gp35 monomer binds gp36 to complete the distal half-fiber; this distal unit then joins the proximal gp34-containing half-fiber. | Genetics, biochemical assembly studies, EM-informed review | Distal half-fiber composition: (gp35)1(gp36)3(gp37)3. | Leiman et al. 2010, *Virology Journal* (Dec 2010), https://doi.org/10.1186/1743-422x-7-355 (pqac-00000001); Hyman & van Raaij 2018, *Biophysical Reviews* (Dec 2018), https://doi.org/10.1007/s12551-017-0348-5 (pqac-00000003) |
| Junction with gp34 | gp36 helps form the connection between the distal and proximal LTF segments; together with gp35 and gp34 C-termini it contributes to the hinge/junction linking the gp34 proximal rod to the gp37-containing distal tip region. | Review of cryo-EM, structural interpretation, bioinformatics | gp36 contributes ~13 nm of the distal portion in one architectural description. | Leiman et al. 2003, *Cell. Mol. Life Sci.* (Nov 2003), https://doi.org/10.1007/s00018-003-3072-1 (pqac-00000000); Hyman & van Raaij 2018, *Biophysical Reviews* (Dec 2018), https://doi.org/10.1007/s12551-017-0348-5 (pqac-00000002) |
| Chaperones gp57A / gp38 | gp57A is a general tail-fiber chaperone required for proper trimerization/folding of gp34 and gp37; gp38 is specifically required for correct folding/assembly of gp37 and is not part of the mature T4 fiber. No gp36-specific dedicated chaperone is identified in these sources. | Genetics, biochemical assembly studies, review | gp57A and gp38 assist assembly but are absent from mature LTF. | Leiman et al. 2010, *Virology Journal* (Dec 2010), https://doi.org/10.1186/1743-422x-7-355 (pqac-00000001, pqac-00000006); Hyman & van Raaij 2018, *Biophysical Reviews* (Dec 2018), https://doi.org/10.1007/s12551-017-0348-5 (pqac-00000003) |
| Structural features of gp36 | gp36 is predicted to be predominantly β-structured, to lack coiled-coil regions, and may contain a novel fold not broadly similar to other known trimeric β-fiber proteins. | Bioinformatics / comparative structural analysis | 221 residues; no coiled-coil regions detected. | Hyman & van Raaij 2018, *Biophysical Reviews* (Dec 2018), https://doi.org/10.1007/s12551-017-0348-5 (pqac-00000002) |
| HHpred similarity segment / interaction inference | HHpred identified a short similarity between gp36 residues 35–61 and gp34 residues 1234–1250, suggesting an interaction-related structural analogy near the gp34 P5/P3–P4 junction and possible gp35-binding architecture at gp34/gp36 ends. | Bioinformatic homology inference linked to known gp34 structure | Similarity segment: gp36 aa 35–61 ↔ gp34 aa 1234–1250. | Hyman & van Raaij 2018, *Biophysical Reviews* (Dec 2018), https://doi.org/10.1007/s12551-017-0348-5 (pqac-00000002) |
| Fiber length / geometry | The full T4 LTF is a long, hinged adhesin assembled from gp34-gp35-gp36-gp37; it consists of two rods joined at an angle and folds against the virion until host encounter. | EM, cryo-EM, review synthesis | Full length ~1440–1450 Å; proximal half ~700 Å; distal half ~740 Å; rod diameter ~40–50 Å; two ~80 nm rods joined at ~160°. | Leiman et al. 2003, *Cell. Mol. Life Sci.* (Nov 2003), https://doi.org/10.1007/s00018-003-3072-1 (pqac-00000000); Leiman et al. 2010, *Virology Journal* (Dec 2010), https://doi.org/10.1186/1743-422x-7-355 (pqac-00000001, pqac-00000012); Hyman & van Raaij 2018, *Biophysical Reviews* (Dec 2018), https://doi.org/10.1007/s12551-017-0348-5 (pqac-00000004) |
| Functional role in adsorption | gp36 is best understood as an internal structural/assembly adaptor within the LTF rather than the principal receptor-binding domain; receptor engagement is concentrated in gp37, while gp36 positions and stabilizes the distal rod for host-search and signaling to the baseplate. | Review synthesis from structural and functional studies | Up to 6 LTFs can engage a cell; receptor-recognition emphasis is on gp37, not gp36. | Hyman & van Raaij 2018, *Biophysical Reviews* (Dec 2018), https://doi.org/10.1007/s12551-017-0348-5 (pqac-00000004); Leiman et al. 2003, *Cell. Mol. Life Sci.* (Nov 2003), https://doi.org/10.1007/s00018-003-3072-1 (pqac-00000005) |
| Infectivity requirement | T4 particles need multiple LTFs for efficient infectivity; long fibers function cooperatively as adsorption/sensing devices before irreversible attachment. | Titration experiments summarized in review | At least 3 long tail fibers are required for infectivity. | Leiman et al. 2010, *Virology Journal* (Dec 2010), https://doi.org/10.1186/1743-422x-7-355 (pqac-00000001) |
| Recent 2023 structural methods | Modern myophage studies combine cryo-EM with AlphaFold-based modeling to reconstruct long tail fibers, providing a methodological template for unresolved proteins like gp36. | 2023 primary cryo-EM study | E217 tail fiber modeled in fragments with AlphaFold; focused tail-fiber map at 3.6 Å; full study used 22,015 micrographs and 10,826 final particles; LPS assay used 10^3 pfu with 500/50/5 µg LPS. | Li et al. 2023, *Nature Communications* (Jul 2023), https://doi.org/10.1038/s41467-023-39756-z (pqac-00000008) |
| Recent 2024 tail-fiber atlas / applications context | RBPseg and the 2024 tail fiber atlas address the difficulty of modeling elongated trimeric RBPs such as T4 LTF proteins, enabling segmentation-based AF2M modeling and classification useful for phage engineering and comparative annotation of gp36-like proteins. | 2024 computational structural biology + cryo-EM validation | 67 fibers analyzed; 16 structural classes; 89 domains; classes cover at least 24% of known tail-fiber universe; 16,345 annotated tail-fiber sequences filtered; 4,417 unique proteins recovered by HMMs (24.0%). | Klein-Sousa et al. 2024, *bioRxiv* (Oct 2024), https://doi.org/10.1101/2024.10.28.620165 (pqac-00000009, pqac-00000010, pqac-00000011) |


*Table: This table summarizes verified evidence about Enterobacteria phage T4 gp36, including its identity, structural role in the long tail fiber, assembly partners, and recent methodological advances relevant to studying gp36-like proteins.*