The Supramolecular Assembly of the Photosynthetic Apparatus of Purple Bacteria Investigated by High-Resolution Atomic Force Microscopy

Abstract

The atomic force microscope (AFM) has developed into a powerful tool in membrane protein research and is now a technique complementary to X-ray crystallography and electron microscopy (EM). The AFM allows high-resolution topographies of biological samples to be acquired under near-physiological conditions, i.e. in buffer solution at ambient temperature and pressure. The exceptionally high signal-to-noise ratio of the AFM allows imaging of single molecules, and it is therefore the only technique to date that can provide structural information on supramolecular membrane protein assemblies in native membranes at nanometer resolution. Hence, AFM can provide images of native membrane organization into which high-resolution membrane protein structures, obtained from X-ray or EM crystallographic studies, can be docked. This chapter will outline recent achievements in the elucidation of the complex assembly of the photosynthetic apparatus in different purple phototrophic bacteria, and discuss feasibilities and restrictions of future applications of AFM in membrane research.