title: Dealing with particles in different conformational states by electron microscopy and image processing.
abstract: Electron microscopy and image processing are powerful tools for investigating different conformational states of enzymes. It is not always possible to isolate these often unstable intermediates as single species. As a result electron micrographs show a snapshot of enzymes in various conformational states. We describe here how to recognize that the imaged particles have different conformations and how to obtain for each species a three-dimensional model using single-particle image processing. We investigated the ATP synthase from chloroplasts, which has a molecular mass of about 550 kDa. It is a membrane-bound enzyme and consists of two segments, a membrane-embedded hydrophobic F(0) part and a hydrophilic F(1) part. Analysis of the particle images indicated that the molecules were in two different conformations. For both conformations three-dimensional models were calculated, which showed that the structures differed mainly in the tilt of the F(0) part with respect to the F(1) part.
authors.affiliation: EMBL Heidelberg, Meyerhofstrasse 1, Heidelberg, 69117, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Mellwig
authors.forename: B
authors.initials: B
authors.lastname: Böttcher
mesh_terms: D025222:Chloroplast Proton-Translocating ATPases / Q000737:chemistry*; D004798:Enzymes / Q000737:chemistry; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D046911:Macromolecular Substances; D008854:Microscopy, Electron / Q000379:methods; D010940:Plant Proteins / Q000737:chemistry; D011487:Protein Conformation; D021122:Protein Subunits
chemical_list: D004798:Enzymes; D046911:Macromolecular Substances; D010940:Plant Proteins; D021122:Protein Subunits; D025222:Chloroplast Proton-Translocating ATPases