Structural biology in vivo through electron cryotomography
In the last ten years electron cryotomography has made it possible to visualize large macromolecular assemblies inside intact cells in a near-native, "frozen-hydrated" state in 3-D to a few nanometers resolution. Increasingly, atomic models of individual proteins and smaller complexes obtained by X-ray crystallography, NMR spectroscopy, or other methods can be fit into cryotomograms to reveal how the various pieces work together inside cells.
A few good pictures is therefore sometimes all that is really needed to distinguish between competing models. To illustrate these points, Dr. Jensen will briefly summarize the key technological advances that have made electron cryotomography possible and then present several examples of current results from his recent work in bacterial cell biology, including new images and mechanistic insights into bacterial chemoreceptor arrays, secretion systems, and the Type IV pilus.
Finally if time permits Dr. Jensen will describe prospects for further improvements, including the possibility of correlated super-resolution light microscopy and nanometer-resolution electron cryotomography of protein complexes in their native state inside intact cells.
About the Speaker
After studying physics and math at Brigham Young University, Grant Jensen earned his doctorate in Biophysics at Stanford working on electron microscopy of RNA polymerase with Dr. Roger Kornberg (who later won the Nobel prize for structural studies of transcription). Grant continued his work in protein electron microscopy as a Damon Runyon-Walter Winchell post-doctoral fellow under the supervision of Dr. Kenneth Downing at the Lawrence Berkeley National Lab. Here his interests expanded to include electron tomography of whole cells. Grant launched his own lab at Caltech starting in 2002. At Caltech his research has focused on three main areas: the ultrastructure of small cells, the structural biology of HIV, and the further development of cryo-EM technology. His lab has now recorded ~25 thousand cryotomograms of over 100 different viral and microbial samples and published ~100 papers. Meanwhile his teaching has centered on biophysical methods, including most recently the creation of a 10-hour online course "Getting started in Cryo-EM." He was chosen as a Searle Scholar in 2004, as Chair of the American Society of Microbiology's Division of Cell and Structural Biology in 2007, and as a Howard Hughes Medical Institute Investigator in 2008.