Side tail fiber protein gpStf is a structural protein that forms four long, thin, jointed side tail fibers on ancestral bacteriophage Ur-lambda virions (disrupted by a laboratory frameshift mutation in lambda PaPa). Twelve copies of gpStf assemble with the assistance of the tail fiber assembly chaperone gpTfa, anchoring via their N-terminal domains (gpStfN) as a dodecameric collar around the junction between the distal hexameric ring of major tail tube protein (gpV) and the hexameric ring of distal tail protein (gpM), while their C-terminal receptor-binding tips reversibly bind the Escherichia coli outer membrane porin OmpC to accelerate primary host adsorption and orient the virion for LamB engagement.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005198 structural molecule activity | IEA GO_REF:0000002 | MODIFY | Summary: General InterPro-derived annotation for structural molecule activity. Reason: Because gpStf is an integral structural subunit of the bacteriophage Ur-lambda virion side tail fibers, GO:0005198 (structural molecule activity) should be refined to its more specific descendant GO:0039660 (structural constituent of virion). Proposed replacements: structural constituent of virion Supporting Evidence: PMID:1439823 The Ur-lambda virions have thin, jointed tail fibers that are absent from lambda wild type. Two novel proteins of Ur-lambda constitute the fibers: the product of stf, the gene that is disrupted in lambda wild type by the frameshift mutation, and the product of gene tfa, a protein that is implicated in facilitating tail fiber assembly. Relative to lambda wild type, Ur-lambda has expanded receptor specificity and adsorbs to Escherichia coli cells more rapidly. PMID:41237242 Twelve copies of gpStfN (gpStf-a, -b, etc.) form a collar that envelops the junction where a ring of six copies of gpV abuts a ring of six copies of gpM in the tail tip complex |
| GO:0019062 virion attachment to host cell | IDA PMID:1439823 Bacteriophage lambda PaPa: not the mother of all lambda phag... | MODIFY | Summary: Experimental demonstration that Ur-lambda side tail fibers (gpStf) accelerate virion adsorption to Escherichia coli. Reason: The side tail fibers formed by gpStf bind the primary adhesion receptor OmpC to accelerate reversible cell-surface attachment without directly triggering genome ejection; refining GO:0019062 to its specific descendant GO:0098671 (adhesion receptor-mediated virion attachment to host cell), already present on this gene, captures this exact role. Proposed replacements: adhesion receptor-mediated virion attachment to host cell Supporting Evidence: PMID:1439823 The Ur-lambda virions have thin, jointed tail fibers that are absent from lambda wild type. Two novel proteins of Ur-lambda constitute the fibers: the product of stf, the gene that is disrupted in lambda wild type by the frameshift mutation, and the product of gene tfa, a protein that is implicated in facilitating tail fiber assembly. Relative to lambda wild type, Ur-lambda has expanded receptor specificity and adsorbs to Escherichia coli cells more rapidly. PMID:41237242 These side fibers, encoded by Ur-λ stf, interact with E. coli OmpC and increase the adsorption rate |
| GO:0019062 virion attachment to host cell | IEA GO_REF:0000120 | MODIFY | Summary: Automated annotation for virion attachment to host cell. Reason: Entailed by the more specific descendant term GO:0098671 (adhesion receptor-mediated virion attachment to host cell) already present on this gene. Proposed replacements: adhesion receptor-mediated virion attachment to host cell Supporting Evidence: PMID:41237242 These side fibers, encoded by Ur-λ stf, interact with E. coli OmpC and increase the adsorption rate |
| GO:0046718 symbiont entry into host cell | IEA GO_REF:0000120 | MODIFY | Summary: Broad automated annotation for viral entry into the host cell. Reason: gpStf participates specifically in the initial adhesion receptor-mediated attachment step of host entry via OmpC binding; refining GO:0046718 to its specific descendant GO:0098671 (already present on this gene) accurately reflects its function. Proposed replacements: adhesion receptor-mediated virion attachment to host cell Supporting Evidence: PMID:41237242 These side fibers, encoded by Ur-λ stf, interact with E. coli OmpC and increase the adsorption rate |
| GO:0046813 receptor-mediated virion attachment to host cell | IDA PMID:30463036 The role of side tail fibers during the infection cycle of p... | MODIFY | Summary: Quantitative live-cell imaging showing that side tail fibers significantly increase Ur-lambda attachment to Escherichia coli cells. Reason: Because gpStf mediates primary reversible attachment via the adhesion receptor OmpC (whereas gpJ mediates irreversible attachment to the entry receptor LamB), GO:0046813 should be refined to its specific descendant GO:0098671 (adhesion receptor-mediated virion attachment to host cell), which is already annotated to this gene. Proposed replacements: adhesion receptor-mediated virion attachment to host cell Supporting Evidence: PMID:30463036 84.0 ± 2.2% (6746 attached phages out of 8034 total phages in 11 experiments) of Ur-λ phages were adsorbed on E. coli host cells, significantly more than 77.3 ± 2.6% (6365 out of 8239 phages in 9 experiments) of λWT phages (Mann-Whitney U-test, p < 0.05) (Fig. 1B). This confirms that the side tail fibers help Ur-λ to encounter the host for infection. |
| GO:0098015 virus tail | IEA GO_REF:0000043 | MODIFY | Summary: General keyword-derived localization to the virus tail. Reason: GO:0098015 (virus tail) is less specific than its part_of descendant GO:0098024 (virus tail, fiber), which is directly supported by experimental electron microscopy and cryo-EM on this gene. Proposed replacements: virus tail, fiber Supporting Evidence: PMID:41237242 Twelve copies of gpStfN (gpStf-a, -b, etc.) form a collar that envelops the junction where a ring of six copies of gpV abuts a ring of six copies of gpM in the tail tip complex |
| GO:0098024 virus tail, fiber | EXP PMID:41237242 Structural basis of bacteriophage Ur-lambda infection initia... | ACCEPT | Summary: Cryo-EM structural resolution of twelve copies of gpStf forming the four side tail fibers anchored at the gpV-gpM junction of Ur-lambda. Reason: High-resolution cryo-EM directly resolves the dodecameric collar formed by the N-terminal domains of gpStf (gpStfN) around the gpV-gpM junction and the four jointed side tail fibers extending from the tail tip complex. Supporting Evidence: PMID:41237242 Twelve copies of gpStfN (gpStf-a, -b, etc.) form a collar that envelops the junction where a ring of six copies of gpV abuts a ring of six copies of gpM in the tail tip complex |
| GO:0098024 virus tail, fiber | IDA PMID:1439823 Bacteriophage lambda PaPa: not the mother of all lambda phag... | ACCEPT | Summary: Electron microscopic and biochemical identification of gpStf as the structural subunit of Ur-lambda side tail fibers. Reason: Hendrix and Duda (1992) demonstrated by electron microscopy and SDS-PAGE of Ur-lambda virions that stf encodes the structural protein of the four thin, jointed side tail fibers. Supporting Evidence: PMID:1439823 The Ur-lambda virions have thin, jointed tail fibers that are absent from lambda wild type. Two novel proteins of Ur-lambda constitute the fibers: the product of stf, the gene that is disrupted in lambda wild type by the frameshift mutation, and the product of gene tfa, a protein that is implicated in facilitating tail fiber assembly. Relative to lambda wild type, Ur-lambda has expanded receptor specificity and adsorbs to Escherichia coli cells more rapidly. |
| GO:0098024 virus tail, fiber | IEA GO_REF:0000043 | ACCEPT | Summary: Keyword-derived localization to the viral tail fiber. Reason: Consistent with direct electron microscopic and cryo-EM evidence showing that gpStf forms the side tail fibers of bacteriophage Ur-lambda. Supporting Evidence: PMID:1439823 The Ur-lambda virions have thin, jointed tail fibers that are absent from lambda wild type. Two novel proteins of Ur-lambda constitute the fibers: the product of stf, the gene that is disrupted in lambda wild type by the frameshift mutation, and the product of gene tfa, a protein that is implicated in facilitating tail fiber assembly. Relative to lambda wild type, Ur-lambda has expanded receptor specificity and adsorbs to Escherichia coli cells more rapidly. |
| GO:0098671 adhesion receptor-mediated virion attachment to host cell | IEA GO_REF:0000043 | ACCEPT | Summary: Primary reversible virion attachment to the host outer membrane adhesion receptor OmpC mediated by gpStf side tail fibers. Reason: Supported by adsorption kinetics, single-particle tracking, and cryo-ET showing that the side tail fibers encoded by stf bind Escherichia coli OmpC as a primary adhesion receptor to accelerate phage capture and position the central fiber gpJ for LamB binding. Supporting Evidence: PMID:41237242 These side fibers, encoded by Ur-λ stf, interact with E. coli OmpC and increase the adsorption rate PMID:30463036 84.0 ± 2.2% (6746 attached phages out of 8034 total phages in 11 experiments) of Ur-λ phages were adsorbed on E. coli host cells, significantly more than 77.3 ± 2.6% (6365 out of 8239 phages in 9 experiments) of λWT phages (Mann-Whitney U-test, p < 0.05) (Fig. 1B). This confirms that the side tail fibers help Ur-λ to encounter the host for infection. file:LAMBD/stf/stf-uniprot.txt CC -!- FUNCTION: Forms tail fibers that play a role in primary attachment of CC virion to host receptors. Assembles with Tail fiber assembly protein to CC form fibers attached to virion tail tip. |
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Download this section (compressed HTML)Q: Does the C-terminal intramolecular chaperone/autoproteolytic domain conserved in phage long tail fibers undergo self-cleavage in Ur-lambda gpStf after gpTfa-assisted trimerization, or does gpTfa remain bound to the mature distal fiber tip in infectious virions?
Experiment: Analyze purified Ur-lambda virions by intact-protein mass spectrometry and cryo-EM focused on the distal C-terminal tips of the side tail fibers in complex with purified OmpC nanodiscs.
Hypothesis: gpTfa chaperones the folding of the OmpC-binding C-terminal tip of trimeric gpStf, and high-resolution reconstruction of the distal fiber-OmpC interface will reveal whether gpTfa is retained as a structural co-subunit or released upon maturation.
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