Professor Brian Crane
Department of Chemistry and Chemical Biology
Cornell University
Ithaca, NY

Monday, October 19, 2015
3:00 pm (CT)
3269 Beckman Institute

Abstract

Bacterial chemotaxis, the ability of bacteria to adapt their motion to external stimuli, has long stood as a model system for understanding transmembrane signaling, intracellular information transfer, and motility. Chemotaxis displays remarkably sensitivity, robustness, and dynamic range. These properties stem from a highly cooperative excitation response and an integral feedback mechanism for adaptation to changing surroundings. Although the molecular components of the chemotaxis system are well characterized, we still do not fully understand the biophysical mechanisms responsible for function. This is because chemotaxis is governed by two highly complex, multi-component, transmembrane assemblies: 1) the sensory apparatus comprised of chemoreceptors, histidine kinases (CheA) and coupling proteins (CheW) and 2) the flagellar motor comprised of rotors, export machinery, ion channels, hooks and filaments. We will discuss efforts to understand the detailed architectures of both systems. Of particular interest are the questions of how chemoreceptors transmit signals across the membrane to regulate CheA activity and how second messenger binding to the flagellar rotor switches the sense of rotation. To address these issues, biophysical studies have been undertaken on isolated components, reconstituted complexes, and native receptor arrays. Evidence will be presented to support the notion that changes to both molecular structure and dynamics are involved in signal transduction and motor output.