Controlling Enzyme Structure and Activity with Light Illumination

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Nanotechnology is implicit in the assembly of proteins into the thousands of active nanostructures pervasive in the human body. The utility of proteins as the building blocks of these bionanomachines derives from the fact that proteins are dynamic entities, responding to molecular interactions in unique and complex ways, often resulting in conformation changes to various non-native or associated states. These conformational transitions influence virtually every biological process. As such, knowledge of both the structure of the non-native states that form in response to various stimuli along with the dynamics of rearrangements between these states is required. This necessitates a means to rapidly induce changes in protein conformation and a method to determine the structure of non-native states (partially-folded or associated) at relatively high resolution. C. Ted Lee, Jr. of the University of Southern California plans to achieve this goal using light-responsive surfactants to induce protein unfolding or association, which will be detected with small-angle neutron scattering (SANS). Surfactants generally affect protein conformation by disrupting intramolecular or intermolecular amino acid contacts, leading to protein unfolding or the dissociation of protein aggregates, respectively. In the case of photoresponsive surfactants, however, the surfactant-amino acid associations can be switched on or off with simple light illumination. This novel method to photo-control protein conformation will be investigated on several length scales. Protein tertiary and quaternary structure will be determined with SANS through shape-reconstruction computational methods to best fit the scattering data, allowing the in vitro protein structure to be determined. SANS experiments require allocation of competitive beam time from a National Laboratory. This proposal requests funds to allow SANS data to be collected on the bioSANS instrument at Oak Ridge National Laboratory from October 14 through 17 of this year with the participation of a graduate student from the Lee Group. These experiments will allow full characterization of the photo-controlled native-to-intermediate-to-denatured or monomer-to-aggregated transitions in proteins. Broader Impacts. Allowing a graduate student to visit ORNL for three days will provide an invaluable experience. In fact, one of the previous students of the PI now currently works at NIST as a result of similar visits. Chemical Engineering education is faced with a curriculum that has become increasingly disconnected with faculty research. To close this gap, proposals such as this travel award will allow a student to work in the atmosphere in the laboratory with ultimate connectability to features of coursework.