An interesting new study has just been published in PLoS Biology on the subject of the remarkable signal transduction circuity responsible for the process of bacterial chemotaxis (a subject that has long fascinated me) and the switching of flagellar rotation direction. The paper is entitled “HAMP Domain Conformers That Propagate Opposite Signals in Bacterial Chemoreceptors,” and the authors provide the following summary:
A central question in biological signal transduction is how cell-surface receptors transmit signals from the outside world across cell membranes and into the cells themselves. In bacteria and lower eukaryotes such receptors are composed of individual modules responsible for specific functions (e.g., sensing, relay, or output). HAMP domains act as the signal relay modules in many receptors, physically bridging input and output components and transferring signals between them. Through a combination of crystallographic, biophysical, spectroscopic, and functional studies we are able to associate two structurally defined HAMP conformational states with functional “on” and “off” signals in bacterial chemoreceptors, and thereby resolve the mechanism by which HAMPs can relay information. The two states differ in both their structure and dynamics and appear to enforce their properties on downstream output modules. Chemoreceptors allow bacteria to track chemical gradients with exquisite sensitivity and dynamic range; we further show that the response to chemoattractant depends critically on specific HAMP residues close to the membrane. Finally, based on the switching mechanism, we design and generate an inverse signaling HAMP domain that provides a new tool to engineer bacterial responses and may be especially advantageous in remediation efforts for directing bacteria towards chemicals that are normally repellants.
Be sure to also check out this report on the study.