Highly ordered protein nanorings designed by accurate control of glutathione S-transferase self-assembly.

Protein self-assembly into exquisite, complex, yet highly ordered architectures represents the supreme wisdom of nature. However, precise manipulation of protein self-assembly behavior in vitro is a great challenge. Here we report that by taking advantage of the cooperation of metal-ion-chelating interactions and nonspecific protein-protein interactions, we achieved accurate control of the orientation of proteins and their self-assembly into protein nanorings. As a building block, we utilized the C2-symmetric protein sjGST-2His, a variant of glutathione S-transferase from Schistosoma japonicum having two properly oriented His metal-chelating sites on the surface. Through synergic metal-coordination and non-covalent interactions, sjGST-2His self-assembled in a fixed bending manner to form highly ordered protein nanorings. The diameters of the nanorings can be regulated by tuning the strength of the non-covalent interaction network between sjGST-2His interfaces through variation of the ionic strength of the solution. This work provides a de novo design strategy that can be applied in the construction of novel protein superstructures.