Crystal structures of Scone, pseudosymmetric folding of a symmetric designer protein

Recent years have seen a raise in the development of computational proteins including symmetric ones. We recently developed a nine-fold symmetric β -propeller protein named Cake. Here we wanted to further engineer this protein to a three-fold symmetric nine-bladed propeller using computational design. Two nine-bladed propeller proteins were designed, named Scone-E and Scone-R. Crystallography however revealed the structure of both designs to adopt an eight-fold conformation with distorted termini, leading to a pseudo-symmetric protein. One of the proteins could only be crystallized upon addition of a polyoxometalate highlighting the usefulness of these molecules as a crystallisation additive.