Beta-propeller

A beta-propeller is a type of all-β protein architecture characterized by 4-8 blade-shaped beta sheets arranged toroidally around a central axis. Each sheet typically has four antiparallel β-strands twisted so that the first and fourth sheets are almost perpendicular to each other. The enzyme's active site is often found in the cleft formed in the center of the propeller by loops connecting the successive four-sheet motifs.

Examples
The influenza virus protein neuraminidase is a six-bladed beta-propeller protein whose active form is a tetramer. It is one of two proteins present in the viral envelope and catalyzes the cleavage of sialic acid moieties from cell-membrane proteins to aid in the targeting of newly produced virions to previously uninfected cells.

WD40 domains, also known as beta-transducin repeats, are short fragments found in eukaryotes but not in prokaryotes. They are often assembled in 4 to 16 repeated units to form a structural domain for critical for protein-protein interactions.