Cryo-EM in the study of membrane transport proteins

Electron cryomicroscopy (cryo-EM) has evolved as a widely used approach to understand a range of structure-function questions, particularly of membrane proteins. Studies by both electron crystallography and single particle analysis have provided a wealth of information on membrane transport proteins. Cryo-EM methods with an emphasis on electron crystallography, which has yielded the most membrane transport protein structural information of any of the cryo-EM techniques, are described here. Two-dimensional crystallization approaches are outlined, as well as advances in cryo-EM specimen preparation, data collection, and image processing. Examples of membrane transport protein structure described serve to illustrate some of the advances in both structural understanding and methods. Further examples outline impressive results that were obtained by a combination of electron crystallography and X-ray crystallography as well as additional complementary methods.