Single-jelly roll vertical
The Single-jelly roll vertical comprises proteins assembling in icosahedral T=13 capsids and composed of a vertical jelly-roll attached to a unique alpha-helix domain. The jelly-roll fold consists of eight beta-strands arranged in two four-stranded sheets.
Topology
The strands are traditionally labeled B through I for the historical reason that the first solved structure, the jelly-roll capsid protein of the tomato bushy stunt virus, had an additional strand A outside the common core of the fold. The sheets are composed of strands BIDG and CHEF, which are folded so that strand B is opposite strand C, I opposite H, and so on.(source wikipedia).
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