Epoxidized graphene grid for high-throughput high-resolution cryoEM structural analysis

Many specimens suffer from low particle density and/or preferred orientation in cryoEM specimen grid preparation, making data collection and structure determination time consuming. We developed an epoxidized graphene grid (EG-grid) that effectively immobilizes protein particles by applying an oxidation reaction using photoactivated ClO2· and further chemical modification. The particle density and orientation distribution are both dramatically improved, having enabled us to reconstruct the density map of GroEL and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), at 1.99 and 2.16 Å resolution from only 504 and 241 micrographs, respectively. A low concentration sample solution of 0.1 mg ml–1 was sufficient to reconstruct a 3.10 Å resolution density map of SARS-CoV-2 spike protein from 1,163 micrographs. The density maps of V1-ATPase, β-galactosidase, and apoferritin were also reconstructed at 3.03, 1.81, and 1.29 Å resolution, respectively. These results indicate that the EG-grid will be a powerful tool for high-throughput cryoEM data collection to accelerate high-resolution structural analysis of biological macromolecules.

De Novo Design of Allosteric Control into Rotary Motor V1-ATPase by Restoring Lost Function

Protein complexes exert various functions through allosterically controlled cooperative work. De novo design of allosteric control into protein complexes provides understanding of their working principles and potential tools for synthetic biology. Here, we hypothesized that an allosteric control can be created by restoring lost functions of pseudo-enzymes contained as subunits in protein complexes. This was demonstrated by computationally de novo designing ATP binding ability of the pseudo-enzyme subunits in a rotary molecular motor, V1-ATPase. Single molecule experiments with solved crystal structures revealed that the designed V1 is allosterically accelerated than the wild-type by the ATP binding to the created allosteric site and the rate is tunable by modulating the binding affinity. This work opened up an avenue for programming allosteric control into proteins exhibiting concerted functions.