Eliminating effects of particle adsorption to the air/water interface in single-particle cryo-electron microscopy: Bacterial RNA polymerase and CHAPSO
Year: 2019
Type: article
Abstract: Preferred particle orientation presents a major challenge for many single particle cryoelectron microscopy (cryo-EM) samples. Orientation bias limits the angular information used to generate three-dimensional maps and thus affects the reliability and interpretability of the structural models. The primary cause of preferred orientation is presumed to be due to adsorption of the particles at the air/water interface during cryo-EM grid preparation. To ameliorate this problem, detergents are often added to cryo-EM samples to alter the properties of the air/water interface. We have found that many bacterial transcription complexes suffer severe orientation bias when examined by cryo-EM. The addition of non-ionic detergents, such as NP-40, does not remove the orientation bias but the Zwitter-ionic detergent CHAPSO significantly broadens the particle orientation distributions, yielding isotropically uniform maps. We used cryoelectron tomography to examine the particle distribution within the ice layer of cryo-EM grid preparations of Escherichia coli 6S RNA/RNA polymerase holoenzyme particles. In the absence of CHAPSO, essentially all of the particles are located at the ice surfaces. CHAPSO at the critical micelle concentration eliminates particle absorption at the air/water interface and allows particles to randomly orient in the vitreous ice layer. We find that CHAPSO eliminates orientation bias for a wide range of bacterial transcription complexes containing E. coli or Mycobacterium tuberculosis RNA polymerases. Findings of this study confirm the presumed basis for how detergents can help remove orientation bias in cryo-EM samples and establishes CHAPSO as a useful tool to facilitate cryo-EM studies of baterial transcription complexes.
Source: Journal of Structural Biology X
Institutions: Rockefeller University, New York Structural Biology Center
Language: English
Subfield: Structural Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,750
Awards: National Resource for Automated Molecular Microscopy, Acquisition of Detector for JEOL 3200 FSC Electron Microscope, G1567773112, Structural Studies of Type II Cadherins on Membranes by Cryo-Electron Tomography, G4845387047, G5004220402, G6128086324, G6269122340, G7229056886, G79964497, G9000128763, Structure, function, and regulation of the bacterial transcription cycle
OpenAlex ID: W2899464734