Baseplate tail-tube junction protein gp54 of bacteriophage T4 that assembles as a homohexameric ring atop the gp48 ring at the apex of the baseplate dome to form the second annulus of the tail-tube continuation. Adopting a tail-tube-like core fold and acting in concert with gp48 and the gp29 tape measure protein, the gp54 hexamer directly nucleates polymerization of the 24 hexameric rings of the major tail tube protein gp19 and contacts the proximal ring of the gp18 contractile sheath.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0098003 viral tail assembly | IEA GO_REF:0000043 | ACCEPT | Reason: gp54 assembles as a homohexameric ring atop gp48 at the top of the baseplate dome to complete baseplate morphogenesis and directly initiate polymerization of the gp19 tail tube. Supporting Evidence: file:BPT4/54/54-uniprot.txt Morphogenesis of the baseplate is completed by association of gp48 and gp54, which bind the upper part of the baseplate dome to form the platform for polymerization of the tail tube. file:BPT4/54/54-deep-research-falcon.md 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. |
| GO:0098015 virus tail | IEA GO_REF:0000043 | MODIFY | Reason: gp54 is specifically localized to the baseplate-tail tube junction at the top of the baseplate dome; the more specific child term GO:0098025 (virus tail, baseplate) is already annotated and directly supported by cryo-EM data. Proposed replacements: virus tail, baseplate Supporting Evidence: file:BPT4/54/54-uniprot.txt Baseplate protein that forms, together with gp48, the baseplate-tail tube junction. The tail tube first 2 annuli are formed by gp48 and gp54, which are in continuation of the spike complex. |
| GO:0098025 virus tail, baseplate | IEA GO_REF:0000043 | ACCEPT | Reason: gp54 is an integral component of the bacteriophage T4 baseplate-tail tube junction, forming the second hexameric annulus atop gp48 at the apex of the baseplate dome. Supporting Evidence: file:BPT4/54/54-uniprot.txt Baseplate protein that forms, together with gp48, the baseplate-tail tube junction. The tail tube first 2 annuli are formed by gp48 and gp54, which are in continuation of the spike complex. file:BPT4/54/54-deep-research-falcon.md 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. |
| GO:0098025 virus tail, baseplate | IDA PMID:27193680 Structure of the T4 baseplate and its function in triggering... | ACCEPT | Reason: Atomic-resolution cryo-EM reconstructions of the 6-MDa T4 baseplate resolve the homohexameric gp54 ring forming the second tube annulus at the top of the baseplate dome. Supporting Evidence: PMID:27193680 Here we present the atomic structure of the approximately 6-megadalton bacteriophage T4 baseplate in its pre- and post-host attachment states and explain the events that lead to sheath contraction in atomic detail. file:BPT4/54/54-uniprot.txt Homohexamer (PubMed:27193680). The tube second annulus is composed of a gp54 hexameric ring. Interacts with the tail tube protein gp19. Interacts with the first layer of sheath proteins gp18. |
Loading supporting content…
Download this section (compressed HTML)Q: Why is monomer-to-hexamer assembly of gp54 strictly dependent on prior binding of the gp48 hexamer to the baseplate dome, given that recombinant gp54 can self-oligomerize at elevated concentrations in vitro?
Q: How do the contacts between the gp54 hexameric ring and the first layer of gp18 sheath subunits rearrange when the sheath detaches from the tube surface during contraction?
Experiment: Determine the cryo-EM structure of the baseplate-tube junction in contracted T4 tails to map how the gp54–gp18 interface is broken while the gp48–gp54–gp19 axial tube continuity is preserved during host envelope puncture.
Experiment: Mutate surface loops on the distal face of the gp54 hexamer to identify the specific residues that lower the nucleation barrier for monomeric gp19 polymerization.
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)