P13341

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research report: Functional annotation of Enterobacteria phage T4 gene 54 (gp54) — UniProt P13341

0) Target verification (critical disambiguation)

The requested target corresponds to Enterobacteria phage T4 (bacteriophage T4) gene product 54 (gp54), a ~35 kDa structural tail protein present in 6 copies per virion and localized at the baseplate–tail tube junction. This matches the UniProt-provided description (“Baseplate tail-tube junction protein gp54”). Multiple independent T4-tail reviews and structural papers agree on the stoichiometry (6) and junction localization, supporting that we are researching the correct protein and not unrelated proteins in other organisms also named “gp54.” (leiman2010morphogenesisofthe pages 2-5, rossmann2004thebacteriophaget4 pages 2-4, leiman2003structureandmorphogenesis pages 7-8)

1) Key concepts and definitions (current understanding)

1.1 What “baseplate–tail tube junction protein” means in T4

In contractile-tailed myophages like T4, the baseplate is a multiprotein assembly at the distal end of the tail that (i) organizes tail morphogenesis and (ii) undergoes conformational changes that trigger sheath contraction during infection. The tail tube (gp19 polymer) is the rigid inner channel for genome passage, surrounded by the contractile sheath (gp18). The baseplate–tail tube junction is the interface where a completed baseplate provides a structural “seat” that initiates polymerization of the tail tube (and indirectly sheath assembly). (rossmann2004thebacteriophaget4 pages 2-4, leiman2003structureandmorphogenesis pages 7-8)

1.2 Functional definition of gp54

Across authoritative sources, gp54 is best defined as a structural assembly initiator/adaptor rather than an enzyme: gp54 (together with gp48) forms a platform at the top of the baseplate hub that initiates oligomerization/polymerization of gp19 tail-tube subunits. (rossmann2004thebacteriophaget4 pages 2-4, yap2016roleofbacteriophage pages 3-5, leiman2003structureandmorphogenesis pages 7-8)

2) Protein function in biological process (morphogenesis and infection pathway)

2.1 Primary function: nucleation of tail tube assembly

A consistent mechanistic model is that gp48 and gp54 create a platform on top of the baseplate hub that initiates gp19 assembly into the tail tube. This is explicitly stated in structural reviews and is supported by cryo-EM-based assignment of the gp48–gp54 region in the baseplate/tail complex. (rossmann2004thebacteriophaget4 pages 2-4, leiman2003structureandmorphogenesis pages 7-8)

Yap et al. further interpret gp54 as having a predicted fold similarity to the tail-tube protein and propose that gp54 (in association with the tape measure/ruler protein gp29) can help initiate gp19 polymerization. This provides an evolutionary/structural rationale for gp54’s initiator role. (yap2016roleofbacteriophage pages 3-5)

2.2 Role in baseplate completion (assembly checkpoint)

T4 baseplate assembly is described as being completed by the binding/attachment of six copies of gp48 and six copies of gp54 at the external interface between the wedge modules and the hub. Only after this step is the baseplate “ready to initiate the tail assembly.” (kostyuchenko2003threedimensionalstructureof pages 1-2, arisaka2016molecularassemblyand pages 2-4, leiman2003structureandmorphogenesis pages 7-8)

2.3 Coupling to sheath initiation (indirect role)

While gp54’s primary role is tube initiation, gp54 participates in a junctional complex that also helps position factors for sheath assembly. Yap et al. report that gp25 binds the gp48–gp54 complex, and because gp25 resembles a domain of the sheath protein gp18, gp25 is proposed to help initiate sheath polymerization after tube initiation. This places gp54 upstream of, and structurally coupled to, the sheath-assembly pathway. (yap2016roleofbacteriophage pages 3-5)

3) Localization and structural context

3.1 Virion localization

Multiple sources explicitly localize gp54 to the “Baseplate–tail tube junction.” (leiman2010morphogenesisofthe pages 2-5, rossmann2004thebacteriophaget4 pages 2-4)

3.2 Stoichiometry and basic protein statistics

Tables in authoritative reviews provide core quantitative descriptors:
- Molecular mass: ~35.0 kDa (gp54 monomer) (leiman2010morphogenesisofthe pages 2-5, rossmann2004thebacteriophaget4 pages 2-4)
- Copy number: 6 copies per tail/virion (leiman2010morphogenesisofthe pages 2-5, rossmann2004thebacteriophaget4 pages 2-4, leiman2003structureandmorphogenesis pages 7-8)
- Oligomeric state: often listed as ND (not determined) in solution in these summaries (leiman2010morphogenesisofthe pages 2-5, rossmann2004thebacteriophaget4 pages 2-4)

3.3 Structural evidence (cryo-EM assignment and resolution)

Early structural placement of the junction region relied on ~12 Å cryo-EM reconstructions of the baseplate/tail tube complex, combined with fitting of known atomic structures and biochemical neighborhood information, allowing assignment of a gp48–gp54–gp19 region at the junction. (rossmann2004thebacteriophaget4 pages 2-4, kostyuchenko2003threedimensionalstructureof pages 1-2)

Later work summarized in Arisaka et al. highlights high-resolution cryo-EM (3.8 Å) of in vitro assembled baseplate-related complexes that refined baseplate assembly models and helped resolve previously unsolved baseplate proteins (including gp48/gp54 in the narrative of the review). (arisaka2016molecularassemblyand pages 2-4)

4) Interaction partners and mechanistic role (evidence-weighted)

The interaction network supported by the retrieved corpus is primarily assembly-pathway and structure-inference based:
- gp48: obligate functional partner at the junction; together they complete baseplate assembly and form the tube-initiation platform. (rossmann2004thebacteriophaget4 pages 2-4, leiman2003structureandmorphogenesis pages 7-8)
- gp19 (tail tube): downstream polymer that is initiated/oligomerized from the gp48–gp54 platform. (rossmann2004thebacteriophaget4 pages 2-4, leiman2003structureandmorphogenesis pages 7-8)
- gp29 (tape measure/ruler protein): proposed association with gp54 in tube initiation (model-based inference). (yap2016roleofbacteriophage pages 3-5)
- gp25: reported to bind the gp48–gp54 complex and proposed to help initiate sheath polymerization (via structural similarity to gp18 domain). (yap2016roleofbacteriophage pages 3-5)

5) Recent developments (prioritizing 2023–2024 sources) — and limitations

The currently retrieved 2023–2024 literature did not provide gp54-specific new measurements for T4 itself; however, it reinforces the broader relevance of T4-like junction/baseplate modules as paradigms:

• Contractile injection systems as antibacterial inspiration (2023): A 2023 cryo-EM/structural study of Vibrio phage XM1 frames contractile tails (phage tails, pyocins, T6SS) as systems that can penetrate bacterial envelopes and “become potential antibacterial agents,” and notes T4 as the best-characterized reference model for Myoviridae tails. This supports ongoing interest in the structural principles embodied by T4 junction/baseplate proteins (including the gp54 functional module), even if XM1 does not directly update T4 gp54. Publication date: 31 Jul 2023; URL: https://doi.org/10.3390/v15081673. (wang2023structureofvibrio pages 1-3)

• Updated baseplate mechanistic paradigms (2024): A 2024 EMBO Journal structural analysis of siphophage JBD30 illustrates modern cryo-EM approaches for describing baseplate-mediated host interactions and infection-cycle transitions (baseplate opening, tape-measure release, genome ejection), providing contemporary context for the continuing centrality of baseplate architectures in infection mechanisms. Publication date: 14 Aug 2024; URL: https://doi.org/10.1038/s44318-024-00195-1. (valentova2024structureandreplication pages 1-2)

• Modern adsorption-focused synthesis (2023): A 2023 Viruses review summarizes adsorption as a multi-step process and emphasizes tail/baseplate proteins as key determinants of host range and infection initiation, contextualizing why baseplate structural modules remain important for applications. Publication date: 10 Jan 2023; URL: https://doi.org/10.3390/v15010196. (leprince2023phageadsorptionto pages 1-2)

Interpretation: recent work is rapidly expanding structural and mechanistic knowledge across diverse phages and contractile systems, but gp54-specific experimental updates appear concentrated in earlier T4-focused structural biology within the retrieved corpus. Therefore, gp54 functional annotation in this report is anchored primarily to the well-established 2003–2016 T4 literature. (arisaka2016molecularassemblyand pages 2-4, yap2016roleofbacteriophage pages 3-5)

6) Current applications and real-world implementations

6.1 Engineering phage assembly experimentally (direct T4-tail implementation)

A concrete experimental implementation relevant to gp54’s neighborhood is plasmid-based expression/complementation of T4 tail/baseplate proteins to enable controlled manipulation of assembly. Duda et al. (1990) showed that expressing structural proteins (demonstrated for gp48; gp54 is part of the same functional junction module in modern models) from plasmids enables complementation in infected cells, immuno-EM localization, and functional testing of engineered variants (internal duplication/length variants), establishing a platform for engineering T4 tail assembly components. Publication date: Dec 1990; URL: https://doi.org/10.1016/0042-6822(90)90140-m. (duda1990expressionofplasmidencoded pages 1-2, duda1990expressionofplasmidencoded pages 5-6)

6.2 Translational framing: CIS-derived antibacterial tools (2023 context)

Recent structural work emphasizes that contractile injection systems can inspire antibacterial tools, even when not directly implemented as therapeutics in the paper. XM1 is discussed as a compact contractile system, and CISs are described as potential antibacterial agents due to their envelope-penetrating capability. (wang2023structureofvibrio pages 1-3)

7) Statistics and data highlights (from the retrieved studies)

Key quantitative/statistical datapoints directly relevant to gp54 annotation:
- gp54: ~35.0 kDa; 6 copies; localization baseplate–tail tube junction (leiman2010morphogenesisofthe pages 2-5, rossmann2004thebacteriophaget4 pages 2-4)
- Baseplate/tail structural context: the baseplate is a large assembly built from six wedges around a hub; a cited cryo-EM reconstruction used ~12 Å resolution to locate components including the gp48/gp54 region (rossmann2004thebacteriophaget4 pages 2-4, kostyuchenko2003threedimensionalstructureof pages 1-2)
- Assembly pathway coupling: gp48/gp54 binding completes baseplate assembly and initiates tail tube assembly; interaction chain includes gp25 as a likely sheath-initiator binding the gp48–gp54 complex (yap2016roleofbacteriophage pages 3-5, leiman2003structureandmorphogenesis pages 7-8)

8) Evidence synthesis table

The following table compiles major gp54 annotation claims, quantitative values, and primary supporting sources.

Table: This table summarizes the main functional annotation evidence for bacteriophage T4 gp54 (UniProt P13341), focusing on location, stoichiometry, assembly role, interaction partners, and structural support. It is useful as a compact evidence map for the final research report.

9) Practical functional annotation summary (for databases)

• Recommended protein name: Baseplate tail-tube junction protein gp54 (gene product 54) (leiman2010morphogenesisofthe pages 2-5, rossmann2004thebacteriophaget4 pages 2-4)
• Molecular function (GO-like): structural molecule activity; tail/baseplate assembly factor; tail tube assembly initiator (rossmann2004thebacteriophaget4 pages 2-4, yap2016roleofbacteriophage pages 3-5)
• Biological process: bacteriophage virion morphogenesis; tail assembly; baseplate completion; initiation of tail tube polymerization (gp19) and coupled initiation of sheath assembly (via gp25) (arisaka2016molecularassemblyand pages 2-4, yap2016roleofbacteriophage pages 3-5, leiman2003structureandmorphogenesis pages 7-8)
• Cellular component (virion location): virion baseplate–tail tube junction (proximal end of tail tube at baseplate interface) (leiman2010morphogenesisofthe pages 2-5)
• Complex/stoichiometry: 6 copies per virion; functions with gp48 in a junctional platform, likely ring-like arrangement consistent with sixfold symmetry (rossmann2004thebacteriophaget4 pages 2-4, yap2016roleofbacteriophage pages 3-5)

10) Key limitations / open needs

Within the retrieved full-text corpus, gp54 lacks (i) a standalone experimentally determined atomic structure and (ii) detailed gp54-specific mutant phenotypes in the extracted passages; many mechanistic claims are supported by cryo-EM placement, assembly-order inference, and structural homology models rather than direct biochemical binding assays for gp54 alone. (kostyuchenko2003threedimensionalstructureof pages 1-2, leiman2010morphogenesisofthe pages 2-5, yap2016roleofbacteriophage pages 3-5)

References

1. (leiman2010morphogenesisofthe pages 2-5): Petr G Leiman, Fumio Arisaka, Mark J van Raaij, Victor A Kostyuchenko, Anastasia A Aksyuk, Shuji Kanamaru, and Michael G Rossmann. Morphogenesis of the t4 tail and tail fibers. Virology Journal, 7:355-355, Dec 2010. URL: https://doi.org/10.1186/1743-422x-7-355, doi:10.1186/1743-422x-7-355. This article has 319 citations and is from a peer-reviewed journal.

2. (rossmann2004thebacteriophaget4 pages 2-4): Michael G Rossmann, Vadim V Mesyanzhinov, Fumio Arisaka, and Petr G Leiman. The bacteriophage t4 dna injection machine. Current opinion in structural biology, 14 2:171-80, Apr 2004. URL: https://doi.org/10.1016/j.sbi.2004.02.001, doi:10.1016/j.sbi.2004.02.001. This article has 250 citations and is from a peer-reviewed journal.

3. (leiman2003structureandmorphogenesis pages 7-8): P. G. Leiman, S. Kanamaru, V. V. Mesyanzhinov, F. Arisaka, and M. G. Rossmann. Structure and morphogenesis of bacteriophage t4. Cellular and Molecular Life Sciences CMLS, 60:2356-2370, Nov 2003. URL: https://doi.org/10.1007/s00018-003-3072-1, doi:10.1007/s00018-003-3072-1. This article has 359 citations.

4. (yap2016roleofbacteriophage pages 3-5): Moh Lan Yap, Thomas Klose, Fumio Arisaka, Jeffrey A. Speir, David Veesler, Andrei Fokine, and Michael G. Rossmann. Role of bacteriophage t4 baseplate in regulating assembly and infection. Proceedings of the National Academy of Sciences, 113:2654-2659, Feb 2016. URL: https://doi.org/10.1073/pnas.1601654113, doi:10.1073/pnas.1601654113. This article has 113 citations and is from a highest quality peer-reviewed journal.

5. (kostyuchenko2003threedimensionalstructureof pages 1-2): Victor A Kostyuchenko, Petr G Leiman, Paul R Chipman, Shuji Kanamaru, Mark J van Raaij, Fumio Arisaka, Vadim V Mesyanzhinov, and Michael G Rossmann. Three-dimensional structure of bacteriophage t4 baseplate. Nature Structural Biology, 10:688-693, Sep 2003. URL: https://doi.org/10.1038/nsb970, doi:10.1038/nsb970. This article has 201 citations.

6. (arisaka2016molecularassemblyand pages 2-4): Fumio Arisaka, Moh Lan Yap, Shuji Kanamaru, and Michael G. Rossmann. Molecular assembly and structure of the bacteriophage t4 tail. Biophysical Reviews, 8:385-396, Nov 2016. URL: https://doi.org/10.1007/s12551-016-0230-x, doi:10.1007/s12551-016-0230-x. This article has 55 citations and is from a peer-reviewed journal.

7. (wang2023structureofvibrio pages 1-3): Zhiqing Wang, Andrei Fokine, Xinwu Guo, Wen Jiang, Michael G. Rossmann, Richard J. Kuhn, Zhu-Hua Luo, and Thomas Klose. Structure of vibrio phage xm1, a simple contractile dna injection machine. Viruses, 15:1673, Jul 2023. URL: https://doi.org/10.3390/v15081673, doi:10.3390/v15081673. This article has 19 citations.

8. (valentova2024structureandreplication pages 1-2): Lucie Valentová, Tibor Füzik, Jiří Nováček, Zuzana Hlavenková, Jakub Pospíšil, and Pavel Plevka. Structure and replication of pseudomonas aeruginosa phage jbd30. The EMBO Journal, 43:4384-4405, Aug 2024. URL: https://doi.org/10.1038/s44318-024-00195-1, doi:10.1038/s44318-024-00195-1. This article has 25 citations.

9. (leprince2023phageadsorptionto pages 1-2): Audrey Leprince and Jacques Mahillon. Phage adsorption to gram-positive bacteria. Viruses, 15:196, Jan 2023. URL: https://doi.org/10.3390/v15010196, doi:10.3390/v15010196. This article has 104 citations.

10. (duda1990expressionofplasmidencoded pages 1-2): Robert L. Duda, Mari Gingery, Lance K Ishimoto, and Frederick A Eiserling. Expression of plasmid-encoded structural proteins permits engineering of bacteriophage t4 assembly. Virology, 179 2:728-37, Dec 1990. URL: https://doi.org/10.1016/0042-6822(90)90140-m, doi:10.1016/0042-6822(90)90140-m. This article has 6 citations and is from a peer-reviewed journal.

11. (duda1990expressionofplasmidencoded pages 5-6): Robert L. Duda, Mari Gingery, Lance K Ishimoto, and Frederick A Eiserling. Expression of plasmid-encoded structural proteins permits engineering of bacteriophage t4 assembly. Virology, 179 2:728-37, Dec 1990. URL: https://doi.org/10.1016/0042-6822(90)90140-m, doi:10.1016/0042-6822(90)90140-m. This article has 6 citations and is from a peer-reviewed journal.

Artifacts

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Citations

1. yap2016roleofbacteriophage pages 3-5
2. arisaka2016molecularassemblyand pages 2-4
3. wang2023structureofvibrio pages 1-3
4. valentova2024structureandreplication pages 1-2
5. leprince2023phageadsorptionto pages 1-2
6. leiman2010morphogenesisofthe pages 2-5
7. leiman2003structureandmorphogenesis pages 7-8
8. kostyuchenko2003threedimensionalstructureof pages 1-2
9. duda1990expressionofplasmidencoded pages 1-2
10. duda1990expressionofplasmidencoded pages 5-6
11. https://doi.org/10.3390/v15081673.
12. https://doi.org/10.1038/s44318-024-00195-1.
13. https://doi.org/10.3390/v15010196.
14. https://doi.org/10.1016/0042-6822(90
15. https://doi.org/10.1186/1743-422x-7-355
16. https://doi.org/10.1016/j.sbi.2004.02.001
17. https://doi.org/10.1038/nsb970
18. https://doi.org/10.1007/s00018-003-3072-1
19. https://doi.org/10.1007/s12551-016-0230-x
20. https://doi.org/10.1073/pnas.1601654113
21. https://doi.org/10.1186/1743-422x-7-355,
22. https://doi.org/10.1016/j.sbi.2004.02.001,
23. https://doi.org/10.1007/s00018-003-3072-1,
24. https://doi.org/10.1073/pnas.1601654113,
25. https://doi.org/10.1038/nsb970,
26. https://doi.org/10.1007/s12551-016-0230-x,
27. https://doi.org/10.3390/v15081673,
28. https://doi.org/10.1038/s44318-024-00195-1,
29. https://doi.org/10.3390/v15010196,