The many blades of the β-propeller proteins: conserved but versatile

The beta-propeller is a highly symmetrical structure with 4-10 repeats of a four-stranded antiparallel beta-sheet motif. Although beta-propeller proteins with different blade numbers all adopt disc-like shapes, they are involved in a diverse set of functions, and defects in this family of proteins have been associated with human diseases. However, it has remained ambiguous how variations in blade number could alter the function of beta-propellers. In addition to the regularly arranged beta-propeller topology, a recently discovered beta-pinwheel propeller has been found. Here, we review the structural and functional diversity of beta-propeller proteins, including beta-pinwheels, as well as recent advances in the typical and atypical propeller structures.