| Claim/annotation | Evidence type | Key quantitative details | Primary sources with year and DOI/URL | Citation IDs |
|---|---|---|---|---|
| Correct target identity: bacteriophage T4 gene product 53 (gp53), a baseplate wedge protein encoded by gene 53 | Structural review; genome review | ~196 aa; 6 copies per baseplate | Arisaka et al., 2016, *Biophysical Reviews*, https://doi.org/10.1007/s12551-016-0230-x; Miller et al., 2003, *Microbiol Mol Biol Rev*, https://doi.org/10.1128/MMBR.67.1.86-156.2003 | (pqac-00000000, pqac-00000008) |
| Virion localization: gp53 is part of each of the six baseplate wedges and sits at the interface between adjacent wedges | Cryo-EM structure; structural review; figure-based localization | 6 wedge-associated copies; located in hubless baseplate wedge model and interwedge region | Yap et al., 2016, *PNAS*, https://doi.org/10.1073/pnas.1601654113; Arisaka et al., 2016, *Biophysical Reviews*, https://doi.org/10.1007/s12551-016-0230-x | (pqac-00000001, pqac-00000014, pqac-00000008) |
| Primary function: gp53 promotes wedge–wedge association/circularization to form the hexagonal baseplate | In vitro assembly; cryo-EM-supported interpretation | Addition of gp53 to gp6-gp7-gp8-gp10 wedge intermediate triggers spontaneous association of six wedges into a baseplate-like hexagon | Yap et al., 2010, *J Mol Biol*, https://doi.org/10.1016/j.jmb.2009.10.071; Arisaka et al., 2016, *Biophysical Reviews*, https://doi.org/10.1007/s12551-016-0230-x | (pqac-00000003, pqac-00000004, pqac-00000008) |
| Ordered assembly role: gp53 is added after gp6 and before gp25 in canonical wedge assembly | In vitro assembly; cryo-EM placement | Assembly order: gp11 → gp10 → gp7 → gp8 → gp6 → gp53 → gp25 | Yap et al., 2010, *J Mol Biol*, https://doi.org/10.1016/j.jmb.2009.10.071; Kostyuchenko et al., 2003, *Nat Struct Biol*, https://doi.org/10.1038/nsb970 | (pqac-00000003, pqac-00000006, pqac-00000007) |
| gp53 stabilizes the core wedge complex together with gp25 | High-resolution baseplate analysis; review | Stabilizes the (gp6)2-gp7-(gp8)2-(gp10)3 wedge complex | Taylor et al., 2016, *Nature*, https://doi.org/10.1038/nature17971 | (pqac-00000002, pqac-00000013) |
| Interwedge clamp role: gp53 holds adjacent wedges together in the assembled baseplate | Cryo-EM figure interpretation; supplementary functional annotation | Figure-based assignment shows gp53 x6 bridging neighboring wedges; Supplementary Table 3 labels gp53 as “Wedge, core”, “bundle clamp”, “sheath platform” | Yap et al., 2016, *PNAS*, https://doi.org/10.1073/pnas.1601654113; Taylor et al., 2016, *Nature* supplementary data, https://doi.org/10.1038/nature17971 | (pqac-00000014, pqac-00000009) |
| Direct interaction network includes gp6 and gp7 across wedge interfaces | Cryo-EM density interpretation; structural analysis | In star-shaped baseplate, gp53 helps hold gp7 helix-turn-helix motifs and two gp6 chains from adjacent wedges together | Aksyuk et al., 2009, *Structure*, https://doi.org/10.1016/j.str.2009.04.005; Yap et al., 2016, *PNAS*, https://doi.org/10.1073/pnas.1601654113 | (pqac-00000005, pqac-00000010, pqac-00000014) |
| Interactions with gp25/gp48/gp18 place gp53 in the tail assembly platform | Cryo-EM density subtraction and contact mapping | gp53 localizes near gp25; gp6 N-terminal domain interacts with gp53, gp25, and gp18; gp6 N-terminus + gp53 + gp48 form platform for first gp18 sheath disk | Aksyuk et al., 2009, *Structure*, https://doi.org/10.1016/j.str.2009.04.005 | (pqac-00000005, pqac-00000010) |
| Role in sheath assembly/triggering: gp53 contributes to the platform that initiates sheath assembly and participates in the interaction network that changes during baseplate rearrangement | Structural analysis; supplementary annotation | Linked to first gp18 disk assembly; Supplementary functional label includes “sheath platform” | Aksyuk et al., 2009, *Structure*, https://doi.org/10.1016/j.str.2009.04.005; Taylor et al., 2016, *Nature* supplementary data, https://doi.org/10.1038/nature17971 | (pqac-00000005, pqac-00000009, pqac-00000010) |
| gp53-containing hubless complexes correspond to a low-energy, post-attachment-like/star-shaped baseplate conformation | In vitro assembly; cryo-EM; review | Hubless star-like complex ~3.3 MDa; map at 3.8 Å; wedge coordinates deposited as PDB 5HX2 and EMDB EMD-8064 | Yap et al., 2016, *PNAS*, https://doi.org/10.1073/pnas.1601654113; Arisaka et al., 2016, *Biophysical Reviews*, https://doi.org/10.1007/s12551-016-0230-x | (pqac-00000001, pqac-00000012, pqac-00000020) |
| Biophysical support for gp53-driven higher-order assembly | Analytical ultracentrifugation and EM | Complete wedge ~15 S; unstable intermediate ~40 S; assembled hexagonal baseplate ~70 S; gp53 addition promotes star-shaped assembly | Yap et al., 2010, *J Mol Biol*, https://doi.org/10.1016/j.jmb.2009.10.071 | (pqac-00000003, pqac-00000011) |
| Structural morphology of gp53 itself | Cryo-EM-derived model / figure interpretation | gp53 shown as a V-shaped monomeric protein in Yap et al. 2016 figures | Yap et al., 2016, *PNAS*, https://doi.org/10.1073/pnas.1601654113 | (pqac-00000014) |
| Domain/family support consistent with UniProt assignment | Supplementary functional annotation / domain assignment | PFAM pf11246; homolog fragments in related contractile systems; supports gp53-family identification | Taylor et al., 2016, *Nature* supplementary data, https://doi.org/10.1038/nature17971 | (pqac-00000009) |


*Table: This table compiles the main functional-annotation claims for bacteriophage T4 gp53 (UniProt P16011) and links each claim to the strongest available structural, biochemical, and review evidence. It is useful for tracing which aspects of gp53 function are directly demonstrated versus inferred from high-resolution baseplate models and assembly experiments.*