This project is aimed at the study of the properties of membrane proteins that underlie important biomedical processes and/or are implicated in health disorders and how they interact with their membrane environments. By means of the latest one and two-dimensional electron-spin resonance (ESR) methodologies and nitroxide spin-labeling methods, we will directly observe significant protein functional changes, and in parallel experiments observe the changes occurring in the dynamic structure of the membrane lipids. This ability to accurately characterize both membrane host and membrane protein is an innovative approach in this project on the role of membrane-protein interactions in the protein's function. Specific projects include the following: Study of the effect of fusion peptides and transmembrane domains on membranes will be continued. Recent results showed that the influenza hemagglutinin (HA) fusion peptide (FP) cooperatively increases ordering of the membrane headgroup region. To determine if this membrane ordering effect is common for other entry of envelope viruses, the effect of HIV gp41 fusion peptide and Ebolavirus internal fusion loop will be studied, including their aggregation. In the second project on the dynamics of antigen-mediated clustering of Immunoglobulin E (IgE)-receptor (FceRI) complexes in membranes, it will be determined how protein-lipid and protein- protein interactions dictate their first steps. This study will build upon our recent successes in developing ESR methods to characterize the changes in membrane structural dynamics upon activation. In a third project, tau, a protein important in neurodegeneration will be studied. The molecular basis for tau interactions (and of its disease-linked mutations) with membranes will be addressed. These studies will benefit from our successful project on another intrinsically disordered protein, alpha synuclein. A fourth project will be directed to deter- mine the effects of bilayer properties on th functional dynamics of the glutamate transporter GltPh, an archael homologue of mammalian glutamate transporters, building on recent ESR studies in these labs. In a fifth project our recent ESR studies on the mechanism of transmembrane signaling in bacterial chemoreceptors will be continued and extended. In particular, the participation of membrane lipids will be addressed, including how the bilayer itself changes upon receptor activation, as well as the concomitant changes within the receptors. In all these studies, the modern ESR techniques of Pulse-Dipolar ESR (PDS) (which includes both double electron-electron resonance (DEER) and Double Quantum Coherence (DQC)-ESR) will be used to characterize membrane protein functional changes, and the techniques of multi-frequency ESR and Two-Dimensional Electron-Electron Double Resonances (2D-ELDOR) will be utilized to characterize the concomitant changes in dynamic structure of the membranes. These studies will involve extensive collaborations with leading research groups. Possible clinical applications include detection of membrane changes during immune response, prevention of viral entry, neurological disorders, and development of anti-microbials.
We are studying structures of proteins and cell membranes, as well as the way proteins interact with other components of cell membranes, such as lipids and cholesterols. Our study will focus on understanding mechanisms by which cells communicate with each other through exchange of cellular components. Disorder in the structure of the proteins and the manner of cell communication may lead to allergic conditions, Alzheimer's and other neurodegenerative diseases, viral and bacterial diseases.
|Lai, Alex L; Freed, Jack H (2014) HIV gp41 fusion peptide increases membrane ordering in a cholesterol-dependent fashion. Biophys J 106:172-81|
|Georgieva, Elka R; Xiao, Shifeng; Borbat, Peter P et al. (2014) Tau binds to lipid membrane surfaces via short amphipathic helices located in its microtubule-binding repeats. Biophys J 107:1441-52|
|Airola, Michael V; Sukomon, Nattakan; Samanta, Dipanjan et al. (2013) HAMP domain conformers that propagate opposite signals in bacterial chemoreceptors. PLoS Biol 11:e1001479|
|Georgieva, Elka R; Borbat, Peter P; Ginter, Christopher et al. (2013) Conformational ensemble of the sodium-coupled aspartate transporter. Nat Struct Mol Biol 20:215-21|
|Yu, Long-Xi; Dzikovski, Boris G; Freed, Jack H (2012) A protocol for detecting and scavenging gas-phase free radicals in mainstream cigarette smoke. J Vis Exp :e3406|
|Chiang, Yun-Wei; Costa-Filho, Antonio J; Baird, Barbara et al. (2011) 2D-ELDOR study of heterogeneity and domain structure changes in plasma membrane vesicles upon cross-linking of receptors. J Phys Chem B 115:10462-9|
|Chiang, Yun-Wei; Freed, Jack H (2011) A new Lanczos-based algorithm for simulating high-frequency two-dimensional electron spin resonance spectra. J Chem Phys 134:034112|
|Ge, Mingtao; Freed, Jack H (2011) Two conserved residues are important for inducing highly ordered membrane domains by the transmembrane domain of influenza hemagglutinin. Biophys J 100:90-7|
|Dzikovski, Boris G; Borbat, Peter P; Freed, Jack H (2011) Channel and nonchannel forms of spin-labeled gramicidin in membranes and their equilibria. J Phys Chem B 115:176-85|
|Bhatnagar, Jaya; Borbat, Peter P; Pollard, Abiola M et al. (2010) Structure of the ternary complex formed by a chemotaxis receptor signaling domain, the CheA histidine kinase, and the coupling protein CheW as determined by pulsed dipolar ESR spectroscopy. Biochemistry 49:3824-41|
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