Conformational changes studied by cryo-electron microscopy

Biological processes involving movement, such as muscle contraction or the opening of an ion channel through a membrane, are mediated through conforma tional changes. These changes often occur in large and flexible macromolecu lar complexes. Cryo-electron microscopy provides a means of capturing diffe rent conformational states of such assemblies. Even if the resulting densit y maps are at low resolution, they can be combined with atomic structures o f subcomplexes or isolated components determined by X-ray crystallography o r NMR. This review presents a brief summary of the principles and recent ad vances in macromolecular structure determination by cryo-electron microscop y.