Investigating the Functional Dynamics of Bacterial Chemoreceptors Using Hydrogen Exchange Mass Spectrometry

Abstract

Bacterial chemotaxis is an ideal system to study the underlying mechanisms involved in transmembrane signaling and signal processing. Bacteria such as E. coli sense chemicals through chemoreceptors, and transmit information from the periplasmic space to the cytosol, to ultimately control the swimming direction of the cell. Chemoreceptors function as large multimeric complexes that also contain a histidine kinase (CheA) and an adaptor protein (CheW). Previously, we and others have shown that the cytoplasmic domain of the receptor is highly dynamic, and small changes in a few amino acids can dramatically stabilize this domain. To investigate whether modulation of cytoplasmic domain dynamics plays a role in the signaling mechanism, we have developed a mass spectrometry method to measure hydrogen exchange of the cytoplasmic domain in active, membrane-bound complexes with CheA and CheW. Our global dynamics data clearly shows that cytoplasmic domain dynamics are significantly reduced in active complexes relative to the non-functional solution state. Current efforts to optimize pepsin digest conditions will enable us to determine whether local dynamics change with signaling state, to provide insight into the role of dynamics in the transmembrane signaling mechanism. This research supported by GM 47601, GM085288, and a Fellowship to Seena Koshy from the University of Massachusetts as part of the Chemistry-Biology Interface Training Program (NRSA T32 GM08515 ).