Localization of E. coli Chemoreceptor Arrays
The bacterial chemotaxis system, a ubiquitous signaling network found in most bacteria, is comprised at its core of a large chemoreceptor cluster found specifically at the cell pole. Despite a wealth of structural and biochemical information on the system's components, it is not clear how the chemoreceptor cluster is reliably targeted to the pole. By bending growing E. coli in agar micro-chambers, we have found that chemoreceptor cluster localization is highly sensitive to membrane curvature within non-polar regions of the cell. Furthermore, the strength of the curvature sensitivity we measured is sufficient to explain reliable polar cluster targeting. We propose that entropic spreading between the transmembrane domains of chemoreceptor trimers of dimers leads to the conical complex observed in structural studies, whose shape in turn induces energetically unfavorable deformations in the membrane. We used the entropic spreading model to engineer curvature sensitivity into a series of synthetic protein complexes that we designed out of long, alpha-helical transmembrane proteins that bind to multivalent protein scaffolds. By altering the connectivity of a complex, we were able to control whether complexes were found preferentially in regions of positive or negative membrane curvature. Entropic spreading presents a novel, and potentially widespread mechanism for membrane curvature sensing and generation.