9TO0

gp13 protein from vB_PagS_MED16 bacteriophage

Summary for 9TO0

• Entry DOI: 10.2210/pdb9to0/pdb
• EMDB information: 56097
• Descriptor: Major tail protein gp13 from vB_PagS_MED16 bacteriophage (1 entity in total)
• Functional Keywords: vb_pags_med16 bacteriophage, bacteriophage tail, viral protein
• Biological source: Pantoea phage vB_PagS_MED16
• Total number of polymer chains: 18
• Total formula weight: 512476.45

Authors

Sasnauskas, G.,Tamulaitiene, G.,Miksys, A.,Poviloniene, S.,Casaite, V.,Meskys, R. (deposition date: 2025-12-16, release date: 2026-09-23)

Primary citation

Poviloniene, S.,Sasnauskas, G.,Tamulaitiene, G.,Labutyte, G.,Talaikis, M.,Miksys, A.,Zajanckauskaite, A.,Truncaite, L.,Meskys, R.,Casaite, V.
The Lord of the Rings: Cysteine bonds crosslink the tail of siphovirus.
Protein Sci., 35:e70784-e70784, 2026

PubMed 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 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.

PubMed: 42742064
DOI: 10.1002/pro.70784

Experimental method

ELECTRON MICROSCOPY (2.9 Å)