1. Biophysical and Biochemical Characterization of Avian Secretory Component Provides Structural Insights into the Evolution of the Polymeric Ig Receptor.

    Journal of Immunology 197(4):1408 (2016) PMID 27412418 PMCID PMC4976031

    The polymeric Ig receptor (pIgR) transports polymeric Abs across epithelia to the mucosa, where proteolytic cleavage releases the ectodomain (secretory component [SC]) as an integral component of secretory Abs, or as an unliganded protein that can mediate interactions with bacteria. SC is conser...
  2. A triarylmethyl spin label for long-range distance measurement at physiological temperatures using T1 relaxation enhancement.

    PMID 27214582 PMCID PMC4958593

    Site-directed spin labeling (SDSL) in combination with electron paramagnetic resonance (EPR) spectroscopy has become an important tool for measuring distances in proteins on the order of a few nm. For this purpose pairs of spin labels, most commonly nitroxides, are site-selectively introduced in...
  3. Steric trapping reveals a cooperativity network in the intramembrane protease GlpG.

    Nature Chemical Biology 12(5):353 (2016) PMID 26999782 PMCID PMC4837050

    Membrane proteins are assembled through balanced interactions among proteins, lipids and water. Studying their folding while maintaining the native lipid environment is necessary but challenging. Here we present methods for analyzing key elements of membrane protein folding including thermodynam...
  4. Conformational Mobility in Cytochrome P450 3A4 Explored by Pressure-Perturbation EPR Spectroscopy.

    Biophysical Journal 110(7):1485 (2016) PMID 27074675 PMCID PMC4833771

    We used high hydrostatic pressure as a tool for exploring the conformational landscape of human cytochrome P450 3A4 (CYP3A4) by electron paramagnetic resonance and fluorescence spectroscopy. Site-directed incorporation of a luminescence resonance energy transfer donor-acceptor pair allowed us to...
  5. The structure and dynamics of secretory component and its interactions with polymeric immunoglobulins.

    eLife 5 (2016) PMID 26943617 PMCID PMC4786434

    As a first-line vertebrate immune defense, the polymeric immunoglobulin receptor (pIgR) transports polymeric IgA and IgM across epithelia to mucosal secretions, where the cleaved ectodomain (secretory component; SC) becomes a component of secretory antibodies, or when unliganded, binds and exclu...
  6. Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser.

    Nature 523(7562):561 (2015) PMID 26200343 PMCID PMC4521999

    G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent pathways. Here we report the crystal structure of a constitutively active form of human rhodopsi...
  7. SIGNAL TRANSDUCTION. Structural basis for nucleotide exchange in heterotrimeric G proteins.

    Science 348(6241):1361 (2015) PMID 26089515 PMCID PMC4968074

    G protein-coupled receptors (GPCRs) relay diverse extracellular signals into cells by catalyzing nucleotide release from heterotrimeric G proteins, but the mechanism underlying this quintessential molecular signaling event has remained unclear. Here we use atomic-level simulations to elucidate t...
  8. Structural Insights into the Dynamic Process of β2-Adrenergic Receptor Signaling.

    Cell 161(5):1101 (2015) PMID 25981665 PMCID PMC4441853

    G-protein-coupled receptors (GPCRs) transduce signals from the extracellular environment to intracellular proteins. To gain structural insight into the regulation of receptor cytoplasmic conformations by extracellular ligands during signaling, we examine the structural dynamics of the cytoplasmi...
  9. Structure-relaxation mechanism for the response of T4 lysozyme cavity mutants to hydrostatic pressure.

    PNAS 112(19):E2437 (2015) PMID 25918400 PMCID PMC4434698

    Application of hydrostatic pressure shifts protein conformational equilibria in a direction to reduce the volume of the system. A current view is that the volume reduction is dominated by elimination of voids or cavities in the protein interior via cavity hydration, although an alternative mecha...
  10. The guanine nucleotide exchange factor Ric-8A induces domain separation and Ras domain plasticity in Gαi1.

    PNAS 112(5):1404 (2015) PMID 25605908 PMCID PMC4321267

    Heterotrimeric G proteins are activated by exchange of GDP for GTP at the G protein alpha subunit (Gα), most notably by G protein-coupled transmembrane receptors. Ric-8A is a soluble cytoplasmic protein essential for embryonic development that acts as both a guanine nucleotide exchange factor (G...
  11. Exploring Structure, Dynamics, and Topology of Nitroxide Spin-Labeled Proteins Using Continuous-Wave Electron Paramagnetic Resonance Spectroscopy.

    Methods in Enzymology 564:59 (2015) PMID 26477248

    Structural and dynamical characterization of proteins is of central importance in understanding the mechanisms underlying their biological functions. Site-directed spin labeling (SDSL) combined with continuous-wave electron paramagnetic resonance (CW EPR) spectroscopy has shown the capability of...
  12. Saturation Recovery EPR and Nitroxide Spin Labeling for Exploring Structure and Dynamics in Proteins.

    Methods in Enzymology 564:3 (2015) PMID 26477246

    Experimental techniques capable of determining the structure and dynamics of proteins are continuously being developed in order to understand protein function. Among existing methods, site-directed spin labeling in combination with saturation recovery (SR) electron paramagnetic resonance spectro...
  13. High-Pressure EPR and Site-Directed Spin Labeling for Mapping Molecular Flexibility in Proteins.

    Methods in Enzymology 564:29 (2015) PMID 26477247

    High hydrostatic pressure is a powerful probe of protein conformational flexibility. Pressurization reveals regions of elevated compressibility, and thus flexibility, within individual conformational states, but also shifts conformational equilibria such that "invisible" excited states become ac...
  14. Differential dynamics of extracellular and cytoplasmic domains in denatured States of rhodopsin.

    Biochemistry (Washington) 53(46):7160 (2014) PMID 25268658 PMCID PMC4245987

    Rhodopsin is a model system for understanding membrane protein folding. Recently, conditions that allow maximally denaturing rhodopsin without causing aggregation have been determined, opening the door to the first structural characterization of denatured states of rhodopsin by nuclear magnetic ...
  15. Stationary-phase EPR for exploring protein structure, conformation, and dynamics in spin-labeled proteins.

    Biochemistry (Washington) 53(45):7067 (2014) PMID 25333901 PMCID PMC4238802

    Proteins tethered to solid supports are of increasing interest in bioanalytical chemistry and protein science in general. However, the extent to which tethering modifies the energy landscape and dynamics of the protein is most often unknown because there are few biophysical methods that can dete...
  16. Long-range distance measurements in proteins at physiological temperatures using saturation recovery EPR spectroscopy.

    Journal of the American Chemical Society 136(43):15356 (2014) PMID 25290172 PMCID PMC4227719

    Site-directed spin labeling in combination with EPR is a powerful method for providing distances on the nm scale in biological systems. The most popular strategy, double electron-electron resonance (DEER), is carried out at cryogenic temperatures (50-80 K) to increase the short spin-spin relaxat...
  17. Structural and energetic determinants of adhesive binding specificity in type I cadherins.

    PNAS 111(40):E4175 (2014) PMID 25253890 PMCID PMC4210030

    Type I cadherin cell-adhesion proteins are similar in sequence and structure and yet are different enough to mediate highly specific cell-cell recognition phenomena. It has previously been shown that small differences in the homophilic and heterophilic binding affinities of different type I fami...
  18. High resolution structure and double electron-electron resonance of the zebrafish voltage-dependent anion channel 2 reveal an oligomeric population.

    Journal of Biological Chemistry 289(18):12566 (2014) PMID 24627492 PMCID PMC4007448

    In recent years, there has been a vast increase in structural and functional understanding of VDAC1, but VDAC2 and -3 have been understudied despite having many unique phenotypes. One reason for the paucity of structural and biochemical characterization of the VDAC2 and -3 isoforms stems from th...
  19. Mapping protein conformational heterogeneity under pressure with site-directed spin labeling and double electron-electron resonance.

    PNAS 111(13):E1201 (2014) PMID 24707053 PMCID PMC3977274

    The dominance of a single native state for most proteins under ambient conditions belies the functional importance of higher-energy conformational states (excited states), which often are too sparsely populated to allow spectroscopic investigation. Application of high hydrostatic pressure increa...
  20. Self-association of arrestin family members.

    Handbook of experimental pharmacology 219:205 (2014) PMID 24292832 PMCID PMC4512752

    Mammals express four arrestin subtypes, three of which have been shown to self-associate. Cone photoreceptor-specific arrestin-4 is the only one that is a constitutive monomer. Visual arrestin-1 forms tetramers both in crystal and in solution, but the shape of its physiologically relevant soluti...