| Aspect | Key findings | Best supporting sources (include DOI/URL and year) |
|---|---|---|
| identity | The target is specifically bacteriophage T4 gene 26 / gp26, annotated in T4 literature as a baseplate gene product and hub-associated assembly factor/protein; Arisaka et al. list gp26 as a 208 aa baseplate hub component with stoichiometry not determined. (pqac-00000001, pqac-00000008, pqac-00000023) | Arisaka et al., *Biophysical Reviews* (2016), DOI: 10.1007/s12551-016-0230-x, https://doi.org/10.1007/s12551-016-0230-x (pqac-00000001, pqac-00000008); Gruidl et al., *Virology* (1991), DOI: 10.1016/0042-6822(91)90852-3, https://doi.org/10.1016/0042-6822(91)90852-3 (pqac-00000023) |
| localization | gp26 localizes to the central hub/baseplate region of the T4 tail; reviews describe the central hub as formed by gp5, gp27, gp29 and probably including gp26 and gp28. It is also detected in purified tube baseplates. (pqac-00000009, pqac-00000010, pqac-00000022, pqac-00000026) | Mesyanzhinov et al., *Biochemistry (Moscow)* (2004), DOI: 10.1007/pl00021751, https://doi.org/10.1007/pl00021751 (pqac-00000009); Orlova, *Bacteriophages* (2012), DOI: 10.5772/34642, https://doi.org/10.5772/34642 (pqac-00000010, pqac-00000026); Ye & Nemoto, *J. Bacteriol.* (2004), DOI: 10.1128/JB.186.18.6335-6339.2004, https://doi.org/10.1128/JB.186.18.6335-6339.2004 (pqac-00000022) |
| role in assembly | Gene 26 is required for morphogenesis of the central part of the baseplate. gene 26 mutants can form 15S arm precursors but accumulate unstable 70S baseplate-like structures lacking the central hub/plug, implying a role in assembly or stabilization of the mature hub. (pqac-00000002, pqac-00000006, pqac-00000020, pqac-00000024) | Kikuchi & King, *J. Mol. Biol.* (1975), DOI: 10.1016/S0022-2836(75)80179-3, https://doi.org/10.1016/S0022-2836(75)80179-3 (pqac-00000002, pqac-00000006, pqac-00000020, pqac-00000024) |
| evidence for virion/baseplate association | Earlier work could not reliably detect gp26 in gels, contributing to uncertainty, but later biochemical analysis of purified tube baseplates identified a ~24 kDa gp26 band by N-terminal sequencing and showed gp26 is released from tube baseplates by 6 M urea, supporting direct baseplate association. (pqac-00000003, pqac-00000004, pqac-00000005, pqac-00000019, pqac-00000022) | Ye & Nemoto, *J. Bacteriol.* (2004), DOI: 10.1128/JB.186.18.6335-6339.2004, https://doi.org/10.1128/JB.186.18.6335-6339.2004 (pqac-00000005, pqac-00000019, pqac-00000022); Lou (2002 thesis excerpt summarizing earlier work) (pqac-00000003, pqac-00000004) |
| processing/mass | The predicted/in vivo-expressed gp26 is ~23.9 kDa, while the mature baseplate-associated species migrates at ~24 kDa and has an N-terminus beginning F-D-V-R-V-G-S-K-I-I-N, indicating removal of the first five residues (MYEYK). Earlier transcription work suggested assembly-linked processing. (pqac-00000005, pqac-00000007, pqac-00000022, pqac-00000023) | Gruidl et al., *Virology* (1991), DOI: 10.1016/0042-6822(91)90852-3, https://doi.org/10.1016/0042-6822(91)90852-3 (pqac-00000007, pqac-00000023); Ye & Nemoto, *J. Bacteriol.* (2004), DOI: 10.1128/JB.186.18.6335-6339.2004, https://doi.org/10.1128/JB.186.18.6335-6339.2004 (pqac-00000005, pqac-00000022) |
| interaction partners/co-released proteins | In urea-treated tube baseplates, gp26 is co-released with gp5, gp29, gp27, gp53, gp3, and gp25, consistent with physical proximity to hub and nearby baseplate proteins. Genetic studies place it in the same hub assembly pathway as gp5, gp27, gp28, gp29, and gp51. (pqac-00000005, pqac-00000022, pqac-00000024) | Ye & Nemoto, *J. Bacteriol.* (2004), DOI: 10.1128/JB.186.18.6335-6339.2004, https://doi.org/10.1128/JB.186.18.6335-6339.2004 (pqac-00000005, pqac-00000022); Kikuchi & King, *J. Mol. Biol.* (1975), DOI: 10.1016/S0022-2836(75)80179-3, https://doi.org/10.1016/S0022-2836(75)80179-3 (pqac-00000024) |
| catalytic vs structural debate | Historical interpretation was conflicting: Kikuchi & King–derived models treated gp26 as possibly catalytic/nonstructural because it was hard to detect in mature particles, whereas later biochemical work directly identified gp26 in tube baseplates, supporting at least some structural/baseplate association. Modern reviews therefore place gp26 in the hub but still note uncertainty in its exact location/function. (pqac-00000017, pqac-00000018, pqac-00000019, pqac-00000021) | Lou (2002 thesis excerpt summarizing older models) (pqac-00000017, pqac-00000018); Ye & Nemoto, *J. Bacteriol.* (2004), DOI: 10.1128/JB.186.18.6335-6339.2004, https://doi.org/10.1128/JB.186.18.6335-6339.2004 (pqac-00000019); Arisaka et al., *Biophysical Reviews* (2016), DOI: 10.1007/s12551-016-0230-x, https://doi.org/10.1007/s12551-016-0230-x (pqac-00000021) |
| quantitative data gaps | Important unknowns remain: stoichiometry/copy number of gp26 in the mature tail is listed as ND; no high-resolution atomic structure, oligomeric state, or definitive placement within the hub is provided in the reviewed sources; no enzymatic activity has been demonstrated. (pqac-00000001, pqac-00000008, pqac-00000021, pqac-00000022) | Arisaka et al., *Biophysical Reviews* (2016), DOI: 10.1007/s12551-016-0230-x, https://doi.org/10.1007/s12551-016-0230-x (pqac-00000001, pqac-00000008, pqac-00000021); Ye & Nemoto, *J. Bacteriol.* (2004), DOI: 10.1128/JB.186.18.6335-6339.2004, https://doi.org/10.1128/JB.186.18.6335-6339.2004 (pqac-00000022) |


*Table: This table compiles the main annotation points for bacteriophage T4 gp26 (gene 26; UniProt P13335), emphasizing identity, localization, assembly role, processing, and unresolved questions. It is useful as a compact evidence map for functional annotation using only the retrieved context-supported sources.*