Journal: Protein Sci / Year: 2026 Title: The Lord of the Rings: Cysteine bonds crosslink the tail of siphovirus. Authors: Simona Povilonienė / Giedrius Sasnauskas / Giedrė Tamulaitienė / Greta Labutytė / Martynas Talaikis / Algirdas Mikšys / Aurelija Zajančkauskaitė / Lidija Truncaitė / Rolandas Meškys / Vida Časaitė Abstract: Long, non-contractile tails composed of helical hexameric protein repeats that assemble into continuous tubular structures characterize siphoviruses. The siphovirus tail tube protein gp39 contains ...Long, non-contractile tails composed of helical hexameric protein repeats that assemble into continuous tubular structures characterize siphoviruses. The siphovirus tail tube protein gp39 contains two cysteine residues per monomer. Cryo-electron microscopy revealed that these cysteines are oriented toward the interface between the rings, which facilitates the formation of inter-ring disulfide bonds. Phylogenetic analysis revealed that in the phage tail tube protein-3 (PF08813) family, only a single branch, representing approximately 14% of its members, contains disulfide bonds within the tubular structure, indicating a clear evolutionary adaptation to stabilize the structure. Structural characterization of gp39 alongside its homolog gp13, which naturally lacks disulfide crosslinks, provided insight into this stabilization strategy. Both gp39 and gp13 can self-assemble into tubular structures independently of disulfide bond formation. When cysteine residues were inserted into gp13 at the same positions as in gp39, disulfide bonds were formed, as confirmed by Raman spectroscopy. Differential scanning fluorimetry further demonstrated that variants containing disulfide bonds exhibit enhanced thermal stability. These results reveal the evolutionary and structural basis by which disulfide bonds ensure the stability of phage tail structures and establish the fundamental principles for the design of robust, thermally stable protein nanotubes.
History
Deposition
Dec 16, 2025
Deposition site: PDBE / Processing site: PDBE
Revision 1.0
Sep 23, 2026
Provider: repository / Type: Initial release
Revision 1.0
Sep 23, 2026
Data content type: EM metadata / Data content type: EM metadata / Provider: repository / Type: Initial release
A: Major tail protein gp13 from vB_PagS_MED16 bacteriophage B: Major tail protein gp13 from vB_PagS_MED16 bacteriophage C: Major tail protein gp13 from vB_PagS_MED16 bacteriophage D: Major tail protein gp13 from vB_PagS_MED16 bacteriophage E: Major tail protein gp13 from vB_PagS_MED16 bacteriophage F: Major tail protein gp13 from vB_PagS_MED16 bacteriophage G: Major tail protein gp13 from vB_PagS_MED16 bacteriophage H: Major tail protein gp13 from vB_PagS_MED16 bacteriophage I: Major tail protein gp13 from vB_PagS_MED16 bacteriophage J: Major tail protein gp13 from vB_PagS_MED16 bacteriophage K: Major tail protein gp13 from vB_PagS_MED16 bacteriophage L: Major tail protein gp13 from vB_PagS_MED16 bacteriophage M: Major tail protein gp13 from vB_PagS_MED16 bacteriophage N: Major tail protein gp13 from vB_PagS_MED16 bacteriophage O: Major tail protein gp13 from vB_PagS_MED16 bacteriophage P: Major tail protein gp13 from vB_PagS_MED16 bacteriophage Q: Major tail protein gp13 from vB_PagS_MED16 bacteriophage R: Major tail protein gp13 from vB_PagS_MED16 bacteriophage
Mass: 28470.914 Da / Num. of mol.: 18 Source method: isolated from a genetically manipulated source Details: Expression tag at the N-terminus / Source: (gene. exp.) Pantoea phage vB_PagS_MED16 (virus) / Gene: gp13 / Production host: Escherichia coli BL21(DE3) (bacteria)
Has protein modification
N
-
Experimental details
-
Experiment
Experiment
Method: ELECTRON MICROSCOPY
EM experiment
Aggregation state: PARTICLE / 3D reconstruction method: helical reconstruction
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Sample preparation
Component
Name: Major tail protein gp13 from vB_PagS_MED16 bacteriophage Type: COMPLEX / Entity ID: all / Source: RECOMBINANT
Source (natural)
Organism: Pantoea phage vB_PagS_MED16 (virus)
Source (recombinant)
Organism: Escherichia coli BL21(DE3) (bacteria)
Buffer solution
pH: 8
Specimen
Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
Electron dose: 30 e/Å2 / Detector mode: COUNTING / Film or detector model: FEI FALCON III (4k x 4k) / Num. of grids imaged: 1 / Num. of real images: 990
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