Membrane Protein Engineering
Nanobiology: Biomimetic nanostructures for membrane protein structure and function
Membrane proteins facilitate many key cellular processes including signal recognition, ion transport, and energy transduction. The study and subsequent exploitation of membrane proteins has, however, received considerably less attention than have soluble proteins, primarily due to difficulties encountered in stabilizing these biological molecules after they are removed from their native lipid bilayer environment. Biomembranes are organized nanospaces which exert control over parameters such as the dimensions available for protein-mediated reactions, the proximity, arrangement, and orientation of the reactants, and the electrostatic and dielectric response of the reaction environment. Collectively, these factors work to control intra- and inter-cellular communication, that is, signal and energy transfer and/or transduction. To fully harness the potential of membrane proteins, there is a need for the development of synthetic, biomembrane-mimetic materials that can house them with retention of native structure and activity while providing a controlled environment amenable to study by a variety of physical techniques.
Via strong collaborations with the laboratory of Millie Firestone in the Materials Science Division at Argonne National Laboratory, we are evaluating an approach to the design, synthesis, and characterization of stimuli-responsive, soft, nanostructured composite materials _ complex fluids _ that can be used to stabilize and organize membrane proteins for structural and functional studies. Because complex fluids comprise mixtures of molecular amphiphiles, their compositions and properties can be readily tuned to allow the stable and ordered incorporation of a wide variety of membrane proteins. Certain forms of these complex fluids exhibit a unique physical property _ a thermoreversible phase transition _ and thus possess a built-in self-repair mechanism. The stimuli-responsive complex fluids developed here offer significant opportunities to employ dynamic architectures as a means to control externally the organization (i.e., internal packing arrangement and orientation) and physical properties of encapsulated “guest” membrane proteins.
Towards this end, our laboratory is in charge of producing and specifically engineering target membrane proteins for incorporation into the soft nanomaterials. We are focusing initially on photoactive reporter proteins with easily assayable functions. We expect to move on rapidly to membrane proteins whose functions are more difficult to assay and membrane protein complexes of defined composition and function.
