Signal transduction in the visual system involves a series of proteins that are sequentially activated via protein-protein interactions, thus passing the signal from the membrane receptor to a final target. The long- term objectives of this project are to elucidate the molecular mechanisms of activation and signal propagation in three proteins of the relay: rhodopsin, transducin and arrestin. It is now abundantly clear that these proteins are highly """"""""flexible"""""""". The flexibility involves ps-ns backbone fluctuations as well as a slower exchange between distinct conformational substates, both being central to function. Thus, mechanisms will not be revealed by structures determined in the confines of a crystal lattice, but will require new spectroscopic methods to complement crystallography and observe the proteins """"""""in action"""""""" in a native-like environment. Toward this goal, one specific aim includes the development and application of new strategies in Site Directed Spin Labeling (SDSL). These include: (1) genetically encoded non-native amino acids for extending SDSL to previously inaccessible proteins and for attaching proteins to solid supports;(2) high pressure Electron Paramagnetic Resonance (EPR) for revealing protein flexibility and low-lying excited states and (3) pulse saturation recovery EPR and pressure-jump relaxation EPR for identifying conformational exchange and measuring exchange rates. Another specific aim is focused on application of these novel technologies together with Double Electron Electron Resonance (DEER) to elucidate structure and the role of dynamics in the activation of the proteins of signal transduction. Goals include a description of: (1) the conformational substates in activated rhodopsin (R*) and the mechanism of constitutive activation;(2) the conformational states of the transducin a-subunit and the structure of the R*-transducin complex and (3) the structure of the R*-arrestin complex, the transformations leading to the high-affinity binding form, and the mechanism of constitutive activation. A growing number of pathological conditions have been traced to genetic defects in the molecular switches of the visual and other signaling systems. In order to design pharmacological approaches for altering such pathological states, it is imperative to understand molecular mechanism involved in the signal relay. Success in this project is anticipated to contribute to this understanding.

Public Health Relevance

A growing number of pathological conditions have been traced to defects in proteins involved in biological signaling. In order to design drugs to effectively correct the defect, it is imperative to understand how the proteins function. Success in this project will contribute substantially to this understanding.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Biochemistry and Biophysics of Membranes Study Section (BBM)
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Neuhold, Lisa
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University of California Los Angeles
Schools of Medicine
Los Angeles
United States
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Kintzer, Alexander F; Green, Evan M; Dominik, Pawel K et al. (2018) Structural basis for activation of voltage sensor domains in an ion channel TPC1. Proc Natl Acad Sci U S A 115:E9095-E9104
Bergdoll, Lucie A; Lerch, Michael T; Patrick, John W et al. (2018) Protonation state of glutamate 73 regulates the formation of a specific dimeric association of mVDAC1. Proc Natl Acad Sci U S A 115:E172-E179
Stadtmueller, Beth M; Bridges, Michael D; Dam, Kim-Marie et al. (2018) DEER Spectroscopy Measurements Reveal Multiple Conformations of HIV-1 SOSIP Envelopes that Show Similarities with Envelopes on Native Virions. Immunity 49:235-246.e4
Gu, Xin; Bridges, Michael D; Yan, Yan et al. (2018) Conformational heterogeneity of the allosteric drug and metabolite (ADaM) site in AMP-activated protein kinase (AMPK). J Biol Chem 293:16994-17007
Van Eps, Ned; Altenbach, Christian; Caro, Lydia N et al. (2018) Gi- and Gs-coupled GPCRs show different modes of G-protein binding. Proc Natl Acad Sci U S A 115:2383-2388
Van Eps, Ned; Caro, Lydia N; Morizumi, Takefumi et al. (2017) Conformational equilibria of light-activated rhodopsin in nanodiscs. Proc Natl Acad Sci U S A 114:E3268-E3275
Zhou, X Edward; He, Yuanzheng; de Waal, Parker W et al. (2017) Identification of Phosphorylation Codes for Arrestin Recruitment by G Protein-Coupled Receptors. Cell 170:457-469.e13
Davydov, Dmitri R; Yang, Zhongyu; Davydova, Nadezhda et al. (2016) Conformational Mobility in Cytochrome P450 3A4 Explored by Pressure-Perturbation EPR Spectroscopy. Biophys J 110:1485-1498
Stadtmueller, Beth M; Yang, Zhongyu; Huey-Tubman, Kathryn E et al. (2016) Biophysical and Biochemical Characterization of Avian Secretory Component Provides Structural Insights into the Evolution of the Polymeric Ig Receptor. J Immunol 197:1408-14
Yang, Zhongyu; Bridges, Michael D; López, Carlos J et al. (2016) A triarylmethyl spin label for long-range distance measurement at physiological temperatures using T1 relaxation enhancement. J Magn Reson 269:50-54

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