Engineering transmembrane signal transduction in synthetic membranes using two-component systems

Abstract

Cells use signal transduction across their membranes to sense and respond to a wide array of chemical and physical signals. Creating synthetic systems which can harness cellular signaling modalities promises to provide a powerful platform for biosensing and therapeutic applications. As a first step towards this goal, we investigated how bacterial two-component systems can be leveraged to enable transmembrane-signaling with synthetic membranes. Specifically, we demonstrate that a bacterial two-component nitrate-sensing system (NarX-NarL) can be reproduced outside of a cell using synthetic membranes and cell-free protein expression systems. We find that performance and sensitivity of the two-component system can be tuned by altering the biophysical properties of the membrane in which the histidine kinase (NarX) is integrated. Through protein engineering efforts, we modify the sensing domain of NarX to generate sensors capable of detecting an array of ligands. Finally, we demonstrate that these systems can sense ligands in relevant sample environments. By leveraging membrane and protein design, this work helps reveal how transmembrane sensing can be recapitulated outside of the cell, adding to the arsenal of deployable cell-free systems primed for real world biosensing. Significance StatementCells detect and respond to environmental and chemical information by using a combination of membrane proteins and genetic polymers. Recapitulation of this behavior in synthetic systems holds promise for engineering biosensors and therapeutics. Using the nitrate-sensing bacterial two-component system as a model, we demonstrate methods to reproduce and tune transmembrane signaling in synthetic lipid membranes, leading to the synthesis of genetically programmed proteins. Through this study, we gain insight into how membrane augmented cell-free systems can be used as a platform to characterize membrane-receptor interactions and engineer new biosensors.