Determining the Dynamic Protein Structure by Individual-Particle Electron Tomography: An Individual Antibody Structure at a Nanometer Resolution

Abstract

Antibodies are naturally dynamic, flexible, and structurally heterogeneous. However, the structural heterogeneity has made difficult the structural and functional study by current technologies, such as X-ray crystallography, NMR and single-particle electron microscopy.Here, we report a method to study the antibody structure. The method, which we called individual-particle electron tomography (IPET), is the combination of current electron tomography (ET) technology with our reconstruction program for resolving the high-resolution structure of an individual particle (see our other abstracts). First, we used ET to image an individual antibody from a series of tilt angles. Then, we tracked the targeted antibody and windowed its images. Finally, we used our local refinement program to reconstruct the three-dimensional (3D) density map of the antibody (Figure). The map contained rich structural details, including the holes in the Fab domains, and was the highest resolution map ever obtained from an individual object (resolution was ∼1nm). Comparing the maps from different antibodies, it allowed us to study antibody dynamics and mobility characteristics. Thus, we propose IPET as a novel method for the structural and functional study of the highly dynamic proteins.View Large Image | View Hi-Res Image | Download PowerPoint Slide