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bioRxiv · 10.1101/2023.06.28.546888

Electron microscopic and crystallographic studies of bacteriophage Sf6 procapsid-like particles assembled from heterologously expressed capsid protein gp5

Tang, L.·Zhao, H.
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Abstract

Many double-stranded DNA (dsDNA) viruses undergo a capsid maturation process during assembly of infectious virus particles, which involves transformation of a metastable capsid precursor called procapsid into a stable, DNA-filled capsid usually with a larger size and a more angular shape. Sf6 is a tailed dsDNA bacteriophage that infects Shigella flexneri. The phage Sf6 capsid protein gp5 was heterologously expressed and purified. Electron microscopy showed that the gp5 spontaneously assembled into spherical, procapsid-like particles. We also observed tube-like and cone-shaped particles reminiscent of human immunodeficiency virus. The gp5 procapsid-like particles were crystallized and crystals diffracted beyond 4.3 [A] resolution. X-ray data at 5.9 [A] resolution were collected with a completeness of 31.1% and an overall Rmerge of 15.0%. The crystals belong to the space group C2 with unit cell dimensions of a=973.326 [A], b=568.234 [A], c=565.567 [A], and {beta}=120.540{degrees}. Self-rotation function showed the 532 symmetry, confirming formation of icosahedral particles. The particle was situated at the origin of the crystal unit cell with the icosahedral 2-fold axis coinciding with the crystallographic b axis, and there is a half of the icosahedral particle in the crystallographic asymmetric unit.

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Tang, L., Zhao, H.. 2023-06-28. Electron microscopic and crystallographic studies of bacteriophage Sf6 procapsid-like particles assembled from heterologously expressed capsid protein gp5. https://doi.org/10.1101/2023.06.28.546888

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