The Unconventional Cytoplasmic Sensing Mechanism for Ethanol Chemotaxis in Bacillus subtilis
Payman Tohidifar, Girija A. Bodhankar, Sichong Pei, C. Keith Cassidy, Hanna E. Walukiewicz, George Ordal, Phillip J. Stansfeld, Christopher V. Rao
Abstract
likely uses ethanol to find ethanol-fermenting microorganisms to utilize as prey. Two chemoreceptors sense ethanol: HemAT and McpB. HemAT's myoglobin-like sensing domain directly binds ethanol, but the heme group is not involved. McpB is a transmembrane receptor consisting of an extracellular sensing domain and a cytoplasmic signaling domain. While most attractants bind the extracellular sensing domain, we found that ethanol directly binds between intermonomer helices of the cytoplasmic signaling domain of McpB, using a mechanism akin to those identified in many mammalian ethanol-binding proteins. Our results indicate that the sensory repertoire of chemoreceptors extends beyond the sensing domain and can directly involve the signaling domain.