Major tail tube protein gp19 of bacteriophage T4 that polymerizes into 24 stacked hexameric rings (144 subunits total) atop the gp48/gp54 baseplate-tube junction platform and around the gp29 tape measure protein to form the rigid central cylinder of the phage tail. Surrounded by the outer contractile gp18 sheath, the gp19 tube is mechanically driven across the host bacterial outer membrane during sheath contraction to form the hollow conduit for viral dsDNA genome ejection into the host cytoplasm.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005198 structural molecule activity | IEA GO_REF:0000002 | MODIFY | Reason: gp19 is specifically a structural component of the mature bacteriophage T4 virion tail tube; the more specific child term GO:0039660 (structural constituent of virion) more precisely captures its molecular function. Proposed replacements: structural constituent of virion Supporting Evidence: PMID:2963141 The nucleotide sequence of gene 19 of bacteriophage T4, the structural gene of the tail tube protein, was determined by both the dideoxy and the Maxam-Gilbert methods. file:BPT4/19/19-uniprot.txt Forms the central cylindrical rigid tube, which is surrounded by the outer contractile sheath assembled from gp18 subunits. |
| GO:0046718 symbiont entry into host cell | IEA GO_REF:0000043 | MODIFY | Reason: Bacteriophage T4 injects its genomic DNA through the gp19 tail tube driven across the host envelope by sheath contraction rather than entering as an intact particle; the more specific child term GO:0099000 (symbiont genome ejection through host cell envelope, contractile tail mechanism) is already annotated and better describes this process. Proposed replacements: symbiont genome ejection through host cell envelope, contractile tail mechanism Supporting Evidence: file:BPT4/19/19-uniprot.txt During infection, contraction of the sheath drives the central tube through the host outer membrane, creating a channel for DNA ejection from the capsid into the host cell. |
| GO:0098015 virus tail | IEA GO_REF:0000043 | MODIFY | Reason: gp19 forms the central rigid tail tube rather than an unspecified part of the tail; the more specific child term GO:0098026 (virus tail, tube) is already present and directly supported. Proposed replacements: virus tail, tube Supporting Evidence: file:BPT4/19/19-uniprot.txt Forms the central cylindrical rigid tube, which is surrounded by the outer contractile sheath assembled from gp18 subunits. |
| GO:0098026 virus tail, tube | IEA GO_REF:0000043 | ACCEPT | Reason: gp19 is the principal structural subunit of the bacteriophage T4 inner tail tube, assembling into 24 stacked hexameric rings. Supporting Evidence: file:BPT4/19/19-uniprot.txt Forms the central cylindrical rigid tube, which is surrounded by the outer contractile sheath assembled from gp18 subunits. file:BPT4/19/19-deep-research-falcon.md T4 gp19 is a structural polymer: it self-assembles into the inner tail tube and provides the physical conduit for dsDNA translocation during infection; it does not catalyze a chemical reaction |
| GO:0099000 symbiont genome ejection through host cell envelope, contractile tail mechanism | IEA GO_REF:0000043 | ACCEPT | Reason: During sheath contraction, the rigid gp19 tail tube is driven through the host outer membrane to form the transmembrane channel through which viral genomic DNA is ejected into the host cell. Supporting Evidence: file:BPT4/19/19-uniprot.txt During infection, contraction of the sheath drives the central tube through the host outer membrane, creating a channel for DNA ejection from the capsid into the host cell. file:BPT4/19/19-deep-research-falcon.md T4 gp19 is a structural polymer: it self-assembles into the inner tail tube and provides the physical conduit for dsDNA translocation during infection; it does not catalyze a chemical reaction |
| GO:0098026 virus tail, tube | IDA PMID:2963141 Nucleotide sequence of the tail tube structural gene of bact... | ACCEPT | Reason: Gene 19 sequencing and direct N- and C-terminal protein chemistry on purified tail tube protein established gp19 as the structural subunit of the T4 tail tube. Supporting Evidence: PMID:2963141 The nucleotide sequence of gene 19 of bacteriophage T4, the structural gene of the tail tube protein, was determined by both the dideoxy and the Maxam-Gilbert methods. |
Loading supporting content…
Download this section (compressed HTML)Q: How does the negatively charged inner lumen of the gp19 hexameric tube modulate the exit of the gp29 tape measure protein and subsequent high-speed translocation of genomic dsDNA during infection?
Q: What conformational signal at the distal gp19 hexameric ring allows the gp15 tail-completion hexamer to bind specifically after 24 rings of gp19 have polymerized around gp29?
Experiment: Perform cryo-EM single-particle reconstruction of the gp54–gp19–gp29 junction and the distal gp19–gp15 cap in intact extended and contracted tails to resolve the exact interface transitions between gp54, gp19, and gp15.
Experiment: Mutate conserved charged residues lining the inner lumen of gp19 and measure DNA ejection kinetics in vitro using liposome-reconstituted outer membrane OmpC/LPS receptors and fluorescent DNA-intercalating dyes.
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)