POSTERS - BLAST X - University of Utah

BLAST X Wed. Morning Session
STRUCTURE, ASSEMBLY AND CONFORMATIONAL CHANGES IN CHEMORECEPTORS
STUDIED IN INTACT BACTERIAL CELLS USING CRYO-ELECTRON TOMOGRAPHY
Cezar M. Khursigara, Xiongwu Wu*, Peijun Zhang, Jon Lefman, Mario J. Borgnia, Yuhai Tu ‡ ,
Jacqueline Milne and Sriram Subramaniam
National Cancer Institute and *National Heart, Lung and Blood Institute, NIH, Bethesda, MD
20892.
‡ T. J. Watson Research Center, IBM, Yorktown Heights, NY 10598
Bacteria respond to changes in their chemical environment by activating an assembly of
proteins that collectively represent the bacterial chemotaxis apparatus. In Gram-negative
bacteria the core-signaling unit of the chemotaxis machinery is a ternary complex composed of
chemoreceptors, CheA and CheW that localize primarily to the poles of the cell and form
extended arrays. Using cryo-electron tomography, we describe and compare the architecture,
localization and spatial relationship between macromolecular complexes involved in chemotaxis
signaling and cellular motility in three different Gram-negative bacteria. In addition, by
combining the tomographic analysis with 3D averaging methods we demonstrate that trimeric
chemoreceptors in E. coli display two distinct conformations that differ principally in
arrangement of the HAMP domains within each trimer.
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