Abstract

With the advent of direct electron detectors, the perspectives of cryo-electron microscopy (cryo-EM) have changed in a profound way. These cameras are superior to previous detectors in coping with the intrinsically low contrast and beam-induced motion of radiation-sensitive organic materials embedded in amorphous ice, and hence they have enabled the structure determination of many macromolecular assemblies to atomic or near-atomic resolution. Nevertheless, there are still limitations and one of them is the size of the target structure. Here, we report the use of a Volta phase plate in determining the structure of human haemoglobin (64 kDa) at 3.2 Å. Our results demonstrate that this method can be applied to complexes that are significantly smaller than those previously studied by conventional defocus-based approaches. Cryo-EM is now close to becoming a fast and cost-effective alternative to crystallography for high-resolution protein structure determination.

Highlights

  • With the advent of direct electron detectors, the perspectives of cryo-electron microscopy have changed in a profound way

  • Protein complexes that have been successfully reconstructed to high resolution by single particle analysis (SPA) have molecular weights of B100 kDa or larger[2]

  • The smallest protein solved to near-atomic resolution by single particle cryo-electron microscopy (cryo-EM) is the 3.8 Å resolution structure of the 93 kDa isocitrate dehydrogenase[2]

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Summary

Introduction

With the advent of direct electron detectors, the perspectives of cryo-electron microscopy (cryo-EM) have changed in a profound way. Protein complexes that have been successfully reconstructed to high resolution by single particle analysis (SPA) have molecular weights of B100 kDa or larger[2]. It was suggested that the structure of 100 kDa proteins could be determined at 3 Å resolution from B10,000 particles.

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