Method to Visualize and Analyze Membrane Interacting Proteins by Transmission Electron Microscopy

J Vis Exp. 2017 Mar 5:(121):55148. doi: 10.3791/55148.

Abstract

Monotopic proteins exert their function when attached to a membrane surface, and such interactions depend on the specific lipid composition and on the availability of enough area to perform the function. Nanodiscs are used to provide a membrane surface of controlled size and lipid content. In the absence of bound extrinsic proteins, sodium phosphotungstate-stained nanodiscs appear as stacks of coins when viewed from the side by transmission electron microscopy (TEM). This protocol is therefore designed to intentionally promote stacking; consequently, the prevention of stacking can be interpreted as the binding of the membrane-binding protein to the nanodisc. In a further step, the TEM images of the protein-nanodisc complexes can be processed with standard single-particle methods to yield low-resolution structures as a basis for higher resolution cryoEM work. Furthermore, the nanodiscs provide samples suitable for either TEM or non-denaturing gel electrophoresis. To illustrate the method, Ca2+-induced binding of 5-lipoxygenase on nanodiscs is presented.

Publication types

  • Video-Audio Media

MeSH terms

  • Cryoelectron Microscopy
  • Lipid Bilayers / chemistry*
  • Membrane Proteins / chemistry*
  • Microscopy, Electron, Transmission / methods*
  • Nanostructures / chemistry

Substances

  • Lipid Bilayers
  • Membrane Proteins