title: Progress and Potential of Electron Cryotomography as Illustrated by Its Application to Bacterial Chemoreceptor Arrays.
abstract: Electron cryotomography (ECT) can produce three-dimensional images of biological samples such as intact cells in a near-native, frozen-hydrated state to macromolecular resolution (∼4 nm). Because one of its first and most common applications has been to bacterial chemoreceptor arrays, ECT's contributions to this field illustrate well its past, present, and future. While X-ray crystallography and nuclear magnetic resonance spectroscopy have revealed the structures of nearly all the individual components of chemoreceptor arrays, ECT has revealed the mesoscale information about how the components are arranged within cells. Receptors assemble into a universally conserved 12-nm hexagonal lattice linked by CheA/CheW rings. Membrane-bound arrays are single layered; cytoplasmic arrays are double layered. Images of in vitro reconstitutions have led to a model of how arrays assemble, and images of native arrays in different states have shown that the conformational changes associated with signal transduction are subtle, constraining models of activation and system cooperativity. Phase plates, better detectors, and more stable stages promise even higher resolution and broader application in the near future.
authors.affiliation: Department of Biology, Leiden University, 2333 Leiden, Netherlands.
authors.forename: Ariane
authors.initials: A
authors.lastname: Briegel
authors.affiliation: Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125; email: jensen@caltech.edu.|Howard Hughes Medical Institute, Pasadena, California 91125.
authors.forename: Grant
authors.initials: G
authors.lastname: Jensen
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002628:Chemoreceptor Cells / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D020285:Cryoelectron Microscopy / Q000379:methods* / Q000639:trends; D009154:Mutation; D040081:Protein Array Analysis; D011487:Protein Conformation; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins
keywords: bacteria; chemotaxis; cryo-EM; imaging; structural biology