Cellular Electron Cryotomography: Toward Structural Biology In Situ
Electron cryotomography (ECT) provides three-dimensional views of macromolecular complexes inside cells in a native frozen–hydrated state. Over the last two decades, ECT has revealed the ultrastructure of cells in unprecedented detail. It has also allowed us to visualize the structures of macromolecular machines in their native context inside intact cells. In many cases, such machines cannot be purified intact for in vitro study. In other cases, the function of a structure is lost outside the cell, so that the mechanism can be understood only by observation in situ. In this review, we describe the technique and its history and provide examples of its power when applied to cell biology. We also discuss the integration of ECT with other techniques, including lower-resolution fluorescence imaging and higherresolution atomic structure determination, to cover the full scale of cellular processes.
© 2017 Annual Reviews. Review in Advance first posted online on April 19, 2017. We apologize to all of our colleagues whose work could not be cited owing to space constraints. We thank Drs. Daniela Nicastro and Andre Hoelz for insightful comments on the manuscript. ECT research in the Jensen laboratory is supported by the National Institutes of Health (R01 grants GM101425 and AI127401 to G.J.J.), the Howard Hughes Medical Institute, the Beckman Institute at Caltech, Caltech's Center for Environmental Microbial Interactions, gifts to Caltech from the Gordon and Betty Moore Foundation and the Agouron Institute, and the John Templeton Foundation as part of the Boundaries of Life project. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. Disclosure Statement: The authors are not aware of any affiliations, memberships, funding, or financial holdings that might be perceived as affecting the objectivity of this review.