Single-Jelly roll fold, horizontal

The single jelly-roll fold consists of eight beta-strands arranged in two four-stranded sheets. It is assembled in T=1,T=3,T=4 or T=7 capsids

Origin:

cellular ancestor

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).