Jelly roll fold

The jelly roll or Swiss roll fold is a protein fold or supersecondary structure composed of eight beta strands arranged in two four-stranded sheets. The name of the structure was introduced by Jane S. Richardson in 1981, reflecting its resemblance to the jelly or Swiss roll cake. The fold is an elaboration on the Greek key motif and is sometimes considered a form of beta barrel. It is very common in viral proteins, particularly viral capsid proteins. Taken together, the jelly roll and Greek key structures comprise around 30% of the all-beta proteins annotated in the Structural Classification of Proteins (SCOP) database.

The basic jelly roll structure consists of eight beta strands arranged in two four-stranded antiparallel beta sheets which pack together across a hydrophobic interface. The strands are traditionally labeled B through H for the historical reason that the first solved structure, of a jelly roll capsid protein from the tomato bushy stunt virus, had an additional strand A outside the fold's common core. The sheets are composed of strands BIDG and CHEF, folded such that strand B packs opposite strand C, I opposite H, etc.

A large number of viruses build their exterior capsids from proteins containing either a single or a double jelly roll fold. This shared capsid architecture is thought to reflect ancient evolutionary relationships, possibly dating to before the last universal common ancestor (LUCA) of cellular life. (Enclosed protein capsids themselves likely evolved at least twice, as other viral lineages use evolutionarily unrelated proteins to build their capsids.)

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