Inner baseplate wedge protein (gp6) of bacteriophage T4 that assembles into a continuous 12-subunit ring of six interdigitated dimers surrounding the central baseplate hub. Within each wedge, a gp6 dimer forms a (gp6)2-gp7 heterotrimeric core module and interacts with gp25 and gp53, while C-terminal dimerization between adjacent wedges ties the six wedges into a circular ring. During the host-attachment-induced dome-to-star transition of the baseplate, a ~15-degree hinge motion between the N- and C-terminal regions of gp6 expands the inner baseplate ring and repositions the gp25-(gp6)2-gp7 module to trigger tail sheath contraction.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0098003 viral tail assembly | IEA GO_REF:0000043 | ACCEPT | Summary: Automated keyword annotation accurately captures the essential role of gp6 in baseplate wedge assembly and tail morphogenesis. Reason: gp6 joins the gp10-gp7-gp8 wedge intermediate to form the (gp6)2-gp7 core and mediates inter-wedge circularization required for baseplate and tail assembly. Supporting Evidence: file:BPT4/6/6-uniprot.txt Baseplate protein that is located next to the tail tube (inner baseplate) (PubMed:27193680). Involved in the tail assembly (PubMed:21129200). The gp25-(gp6)2-gp7 module is involved in sheath contraction (PubMed:27193680). file:BPT4/6/6-deep-research-falcon.md In the mature, dome-shaped T4 baseplate, gp6 is present as a **ring of six gp6 dimers** (i.e., 12 gp6 monomers) surrounding the central hub |
| GO:0098015 virus tail | IEA GO_REF:0000043 | MODIFY | Summary: Correct parent cellular component term that should be refined to the baseplate subcompartment. Reason: Within the virion tail, gp6 localizes specifically to the inner ring of the baseplate (GO:0098025). Proposed replacements: virus tail, baseplate Supporting Evidence: file:BPT4/6/6-uniprot.txt Note=12 copies of gp6 form a continuous ring that makes up most of the inner baseplate. file:BPT4/6/6-deep-research-falcon.md In the mature, dome-shaped T4 baseplate, gp6 is present as a **ring of six gp6 dimers** (i.e., 12 gp6 monomers) surrounding the central hub |
| GO:0098025 virus tail, baseplate | IEA GO_REF:0000120 | ACCEPT | Summary: Automated annotation accurately places gp6 in the viral tail baseplate. Reason: Twelve copies of gp6 form the continuous inner ring of the bacteriophage T4 baseplate. Supporting Evidence: file:BPT4/6/6-uniprot.txt Note=12 copies of gp6 form a continuous ring that makes up most of the inner baseplate. file:BPT4/6/6-deep-research-falcon.md In the mature, dome-shaped T4 baseplate, gp6 is present as a **ring of six gp6 dimers** (i.e., 12 gp6 monomers) surrounding the central hub |
| GO:0042802 identical protein binding | IPI PMID:19523898 The structure of gene product 6 of bacteriophage T4, the hin... | KEEP AS NON CORE | Summary: Crystallographic and cryo-EM analysis demonstrates that gp6 forms both intra-wedge N-terminal homodimers and inter-wedge C-terminal homodimers. Reason: Aksyuk et al. (2009) determined the crystal structure of the C-terminal dimerization region of gp6 and showed how six gp6 dimers interdigitate via N- and C-terminal homodimeric interfaces; retained as a non-core binding term. Supporting Evidence: PMID:19523898 Six gp6 dimers interdigitate, forming a ring that maintains the integrity of the baseplate in both conformations. One baseplate wedge contains an N-terminal dimer of gp6, whereas neighboring wedges are tied together through the C-terminal dimer of gp6. file:BPT4/6/6-deep-research-falcon.md In the mature, dome-shaped T4 baseplate, gp6 is present as a **ring of six gp6 dimers** (i.e., 12 gp6 monomers) surrounding the central hub |
| GO:0098025 virus tail, baseplate | IDA PMID:2403438 Structure of the bacteriophage T4 baseplate as determined by... | ACCEPT | Summary: Chemical cross-linking of intact T4 baseplates and tails directly established gp6 as an inner baseplate component contacting the central hub. Reason: Watts and Coombs (1990) identified near-neighbor cross-links between gp6 in the baseplate wedges and gp27 in the central hub. Supporting Evidence: PMID:2403438 Most of the previous contacts were confirmed, and we report several new contacts, including those within the central hub (gp5-gptd2, gp26-gptd), between the hub and the outer wedges (gp6-gp27(2], between baseplate and sheath (gp54-gp18), and between sheath and core (gp19-gp18). file:BPT4/6/6-deep-research-falcon.md In the mature, dome-shaped T4 baseplate, gp6 is present as a **ring of six gp6 dimers** (i.e., 12 gp6 monomers) surrounding the central hub |
| GO:0098025 virus tail, baseplate | IDA PMID:27193680 Structure of the T4 baseplate and its function in triggering... | ACCEPT | Summary: Atomic cryo-EM structures of the T4 baseplate in pre- and post-attachment states directly resolve the 12-subunit gp6 ring in the inner baseplate. Reason: Taylor et al. (2016) resolved the full-length gp6 structure within the baseplate and defined the role of the gp25-(gp6)2-gp7 module in triggering sheath contraction. 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:BPT4/6/6-uniprot.txt each gp6 molecule in the ring interacts with its two neighbors, forming an N-terminal dimer with one and a C-terminal dimer with the other (PubMed:27193680). Heterotrimer with gp7; gp6 is part of a (gp6)2-gp7 heterotrimeric molecule (PubMed:27193680). file:BPT4/6/6-deep-research-falcon.md In the mature, dome-shaped T4 baseplate, gp6 is present as a **ring of six gp6 dimers** (i.e., 12 gp6 monomers) surrounding the central hub |
| GO:0039660 structural constituent of virion | IDA PMID:27193680 Structure of the T4 baseplate and its function in triggering... | NEW | Summary: Twelve copies of gp6 form an interdigitated ring of six dimers that serves as a core structural scaffold of the bacteriophage T4 baseplate wedge and virion tail. Reason: Atomic-resolution cryo-EM reconstructions of the T4 baseplate (PMID:27193680) and crystallographic analysis (PMID:19523898) demonstrate that gp6 is an essential structural component of the virion baseplate that maintains baseplate ring integrity before and after sheath contraction. 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. PMID:19523898 Six gp6 dimers interdigitate, forming a ring that maintains the integrity of the baseplate in both conformations. One baseplate wedge contains an N-terminal dimer of gp6, whereas neighboring wedges are tied together through the C-terminal dimer of gp6. |
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Download this section (compressed HTML)Q: How does binding of the gp8 homodimer to the gp10-gp7 wedge intermediate chaperone or orient the gp7 alpha-helix so that the (gp6)2 dimer can form the triple-helical bundle of the (gp6)2-gp7 heterotrimer?
Suggested experts: Petr G. Leiman, Fumio Arisaka, Shuji Kanamaru
Q: Does restricting the ~15-degree internal hinge motion between the N- and C-terminal halves of gp6 abolish the dome-to-star transition, or does it uncouple outer wedge rotation from gp25-gp18 sheath contraction?
Suggested experts: Petr G. Leiman, Nicholas M. I. Taylor
Experiment: Engineer disulfide cross-links across the internal hinge region between the N- and C-terminal domains of gp6 and assay baseplate assembly, short tail fiber deployment, and tail sheath contraction under oxidizing versus reducing conditions.
Hypothesis: Locking the gp6 internal hinge will allow normal wedge circularization into a dome-shaped baseplate but prevent the ~10 A radial ring expansion required to trigger gp18 sheath contraction upon host adsorption.
Type: Disulfide-trapping mutagenesis and cryo-EM conformational assay
Experiment: Perform in vitro reconstitution of the (gp6)2-gp7-gp8-gp10 wedge complex with truncated gp6 N-terminal or C-terminal dimerization mutants analyzed by native mass spectrometry and analytical ultracentrifugation.
Hypothesis: Disruption of the N-terminal dimer interface prevents incorporation of gp6 into individual wedges, whereas disruption of the C-terminal dimer interface permits monomeric wedge completion but blocks assembly of the six-wedge circular ring.
Type: Native mass spectrometry and analytical ultracentrifugation of wedge assembly intermediates
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