ジャーナル: Nat Commun / 年: 2025 タイトル: Stabilization mechanism accommodating genome length variation in evolutionarily related viral capsids. 著者: Jennifer M Podgorski / Joshua Podgorski / Lawrence Abad / Deborah Jacobs-Sera / Krista G Freeman / Colin Brown / Graham F Hatfull / Antoni Luque / Simon J White / 要旨: Tailed bacteriophages are one of the most numerous and diverse group of viruses. They store their genome at quasi-crystalline densities in capsids built from multiple copies of proteins adopting the ...Tailed bacteriophages are one of the most numerous and diverse group of viruses. They store their genome at quasi-crystalline densities in capsids built from multiple copies of proteins adopting the HK97-fold. The high density of the genome exerts an internal pressure, requiring a maturation process that reinforces their capsids. However, it is unclear how capsid stabilization strategies have adapted to accommodate the evolution of larger genomes in this virus group. Here we characterize a capsid reinforcement mechanism in two evolutionary-related actinobacteriophages that modifies the length of a stabilization protein to accommodate a larger genome while maintaining the same capsid size. We use cryo-EM to reveal that capsids contain split hexamers of HK97-fold proteins with a stabilization protein in the chasm. The observation of split hexamers in mature capsids is unprecedented, so we rationalize this result mathematically, discovering that icosahedral capsids can be formed by all split or skewed hexamers as long as their T-number is not a multiple of three. Our results suggest that analogous stabilization mechanisms can be present in other icosahedral capsids, and they provide a strategy for engineering capsids accommodating larger DNA cargoes as gene delivery systems.
A: Major capsid protein B: Major capsid protein C: Major capsid protein D: Major capsid protein E: Major capsid protein F: Major capsid protein G: Major capsid protein 3: gp_16 (Minor Capsid Protein) 2: gp_16 (Minor Capsid Protein) 1: gp_16 (Minor Capsid Protein) Y: HNH endonuclease Z: HNH endonuclease 6: gp_16 (Minor Capsid Protein) 5: gp_16 (Minor Capsid Protein) 4: gp_16 (Minor Capsid Protein) 7: gp_16 (Minor Capsid Protein)
A: Major capsid protein B: Major capsid protein C: Major capsid protein D: Major capsid protein E: Major capsid protein F: Major capsid protein G: Major capsid protein 3: gp_16 (Minor Capsid Protein) 2: gp_16 (Minor Capsid Protein) 1: gp_16 (Minor Capsid Protein) Y: HNH endonuclease Z: HNH endonuclease 6: gp_16 (Minor Capsid Protein) 5: gp_16 (Minor Capsid Protein) 4: gp_16 (Minor Capsid Protein) 7: gp_16 (Minor Capsid Protein)
A: Major capsid protein B: Major capsid protein C: Major capsid protein D: Major capsid protein E: Major capsid protein F: Major capsid protein G: Major capsid protein 3: gp_16 (Minor Capsid Protein) 2: gp_16 (Minor Capsid Protein) 1: gp_16 (Minor Capsid Protein) Y: HNH endonuclease Z: HNH endonuclease 6: gp_16 (Minor Capsid Protein) 5: gp_16 (Minor Capsid Protein) 4: gp_16 (Minor Capsid Protein) 7: gp_16 (Minor Capsid Protein)
x 5
icosahedral pentamer
2.14 MDa, 80 ポリマー
分子量 (理論値)
分子数
合計 (水以外)
2,137,201
80
ポリマ-
2,137,201
80
非ポリマー
0
0
水
0
タイプ
名称
対称操作
数
identity operation
1_555
x,y,z
1
point symmetry operation
4
4
A: Major capsid protein B: Major capsid protein C: Major capsid protein D: Major capsid protein E: Major capsid protein F: Major capsid protein G: Major capsid protein 3: gp_16 (Minor Capsid Protein) 2: gp_16 (Minor Capsid Protein) 1: gp_16 (Minor Capsid Protein) Y: HNH endonuclease Z: HNH endonuclease 6: gp_16 (Minor Capsid Protein) 5: gp_16 (Minor Capsid Protein) 4: gp_16 (Minor Capsid Protein) 7: gp_16 (Minor Capsid Protein)
詳細: Standard CTF correction inside RELION's reconstruction. タイプ: PHASE FLIPPING AND AMPLITUDE CORRECTION
対称性
点対称性: I (正20面体型対称)
3次元再構成
解像度: 2.66 Å / 解像度の算出法: FSC 0.143 CUT-OFF / 粒子像の数: 44239 / 対称性のタイプ: POINT
原子モデル構築
プロトコル: AB INITIO MODEL 詳細: Amino acid sequence built into the map for a single major capsid protein and refined with Phenix. Model then used for rest of asymmetric unit and refined with Phenix. Final step involved using Isolde.