Structural characterization of components of the Frz chemoreceptor complex of Myxococcus xanthus

Abstract

In bacterial chemosensory systems, chemoreceptors, called methyl accepting chemosensory proteins (MCPs) are typically involved in sensing environmental cues. MCPs forms arrays on the bacterial membrane, which results in environmental signal amplification and transduction. However, the Myxococcus xanthus chemoreceptor, FrzCD binds DNA instead of the bacterial membrane and uses the bacterial nucleoid as the scaffold for signal transduction. The mechanism of signal transduction is not well studied in such atypical chemoreceptors. In order to characterize the structural basis of signal transduction in FrzCD, the aim is to obtain the structure of FrzCD in complex with downstream signalling components of the Frz chemosensory pathway, such as FrzA. Minimal constructs of FrzCD have been designed and co-transformed with downstream adaptor protein FrzA. Co-purification of FrzA with the coiled coil domain of FrzCD, lacking disordered DNA binding domain, has made the purified protein complex amenable to crystallization. Conditions for crystallizing the complex have been optimized and protein crystals from the purified complex have been obtained. Structure determination using X-ray crystallography of the macromolecular complex will give insights about the interaction and stoichiometry of the protein complex. The structural information would have the potential to help in the structure and function characterization of the Frz chemosensory system.