Tail tape measure protein (TMP) gp29 of bacteriophage T4 that anchors in the central hub of the baseplate and extends through the internal lumen of the growing tail tube during morphogenesis. Working in concert with the gp48/gp54 baseplate-tube junction rings, gp29 nucleates polymerization of the major tail tube protein gp19 and acts as a physical molecular ruler that arrests tube elongation after 24 hexameric rings once gp29 is fully extended.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0098003 viral tail assembly | IEA GO_REF:0000043 | ACCEPT | Reason: gp29 is an essential structural component of the central baseplate hub and the inner tail tube lumen that initiates gp19 polymerization and determines the exact length of the assembled phage tail tube. Supporting Evidence: file:BPT4/29/29-uniprot.txt FUNCTION: Serves as a base for tail tube protein polymerization and acts as a template for tail length determination. file:BPT4/29/29-deep-research-falcon.md A dedicated T4 tail morphogenesis review states that tail tube polymerization stops when gp29 is fully extended and explicitly identifies gp29 as the tape measure protein. |
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Download this section (compressed HTML)Q: What is the exact copy number (trimer vs. hexamer) and C-terminal anchoring interface of gp29 within the (gp5-gp27)3 / gp48 / gp54 baseplate hub dome?
Q: Is gp29 ejected into the host bacterial envelope or cytoplasm ahead of the viral dsDNA genome during infection, and does it form part of the inner-membrane translocation conduit?
Experiment: Construct internal coiled-coil deletions and duplications in gene 29 of bacteriophage T4 and measure the resulting tail tube ring counts and lengths by cryo-EM to directly test the linear ruler relationship between gp29 length and gp19/gp18 ring number.
Experiment: Perform symmetry-expanded focused cryo-EM refinement of the T4 tail tube lumen and baseplate hub junction to resolve the oligomeric stoichiometry and C-terminal anchor of gp29.
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