Atomic Force Microscopy Imaging of Xenopus laevis Oocyte Plasma Membrane

This chapter describes the application of atomic force microscopy (AFM) to the study of the Xenopus laevis oocyte plasma membrane. Different sample preparation protocols developed and optimized to perform AFM investigation of both external and intracellular sides of the oocyte native plasma membrane are presented and discussed. AFM imaging allowed visualization and dimensional characterization of protein complexes observed on both sides of the oocyte plasma membrane. In addition, a methodological approach based on the purification of oocyte plasma membrane by ultracentrifugation on a discontinuous sucrose gradient allowed to image oocyte membrane in a physiological-like environment as well as to identify a membrane protein, the human aquaporin 4, expressed in the oocytes. Taken together, these results confirm the potential of AFM as an useful tool for the structural characterization of proteins in native eukaryotic membranes as well as its relevance for describing the organization of protein complexes in native biological membranes.