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Hee Jung Choi

Bio: Hee Jung Choi is an academic researcher from Seoul National University. The author has contributed to research in topics: G protein-coupled receptor & Wnt signaling pathway. The author has an hindex of 24, co-authored 64 publications receiving 10812 citations. Previous affiliations of Hee Jung Choi include Stanford University & UPRRP College of Natural Sciences.


Papers
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Journal ArticleDOI
23 Nov 2007-Science
TL;DR: Although the location of carazolol in the β2-adrenergic receptor is very similar to that of retinal in rhodopsin, structural differences in the ligand-binding site and other regions highlight the challenges in using rhodopin as a template model for this large receptor family.
Abstract: Heterotrimeric guanine nucleotide–binding protein (G protein)–coupled receptors constitute the largest family of eukaryotic signal transduction proteins that communicate across the membrane. We report the crystal structure of a human β2-adrenergic receptor–T4 lysozyme fusion protein bound to the partial inverse agonist carazolol at 2.4 angstrom resolution. The structure provides a high-resolution view of a human G protein–coupled receptor bound to a diffusible ligand. Ligand-binding site accessibility is enabled by the second extracellular loop, which is held out of the binding cavity by a pair of closely spaced disulfide bridges and a short helical segment within the loop. Cholesterol, a necessary component for crystallization, mediates an intriguing parallel association of receptor molecules in the crystal lattice. Although the location of carazolol in the β2-adrenergic receptor is very similar to that of retinal in rhodopsin, structural differences in the ligand-binding site and other regions highlight the challenges in using rhodopsin as a template model for this large receptor family.

3,065 citations

Journal ArticleDOI
15 Nov 2007-Nature
TL;DR: In this paper, the human beta2 adrenoceptor (beta2AR) was crystallized in a lipid environment when bound to an inverse agonist and in complex with a Fab that binds to the third intracellular loop.
Abstract: Structural analysis of G-protein-coupled receptors (GPCRs) for hormones and neurotransmitters has been hindered by their low natural abundance, inherent structural flexibility, and instability in detergent solutions. Here we report a structure of the human beta2 adrenoceptor (beta2AR), which was crystallized in a lipid environment when bound to an inverse agonist and in complex with a Fab that binds to the third intracellular loop. Diffraction data were obtained by high-brilliance microcrystallography and the structure determined at 3.4 A/3.7 A resolution. The cytoplasmic ends of the beta2AR transmembrane segments and the connecting loops are well resolved, whereas the extracellular regions of the beta2AR are not seen. The beta2AR structure differs from rhodopsin in having weaker interactions between the cytoplasmic ends of transmembrane (TM)3 and TM6, involving the conserved E/DRY sequences. These differences may be responsible for the relatively high basal activity and structural instability of the beta2AR, and contribute to the challenges in obtaining diffraction-quality crystals of non-rhodopsin GPCRs.

1,823 citations

Journal ArticleDOI
13 Jan 2011-Nature
TL;DR: A camelid antibody fragment to the human β2 adrenergic receptor is generated, and an agonist-bound, active-state crystal structure of the receptor-nanobody complex is obtained, providing insights into the process of agonist binding and activation.
Abstract: G protein coupled receptors (GPCRs) exhibit a spectrum of functional behaviours in response to natural and synthetic ligands. Recent crystal structures provide insights into inactive states of several GPCRs. Efforts to obtain an agonist-bound active-state GPCR structure have proven difficult due to the inherent instability of this state in the absence of a G protein. We generated a camelid antibody fragment (nanobody) to the human b2 adrenergic receptor (b2AR) that exhibits G protein-like behaviour, and obtained an agonist-bound, active-state crystal structure of the receptor-nanobody complex. Comparison with the inactive b2AR structure reveals subtle changes in the binding

1,558 citations

Journal ArticleDOI
23 Nov 2007-Science
TL;DR: Analysis of adrenergic receptor ligand-binding mutants within the context of the reported high-resolution structure of β2AR-T4L provides insights into inverse-agonist binding and the structural changes required to accommodate catecholamine agonists.
Abstract: The beta2-adrenergic receptor (beta2AR) is a well-studied prototype for heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) that respond to diffusible hormones and neurotransmitters. To overcome the structural flexibility of the beta2AR and to facilitate its crystallization, we engineered a beta2AR fusion protein in which T4 lysozyme (T4L) replaces most of the third intracellular loop of the GPCR ("beta2AR-T4L") and showed that this protein retains near-native pharmacologic properties. Analysis of adrenergic receptor ligand-binding mutants within the context of the reported high-resolution structure of beta2AR-T4L provides insights into inverse-agonist binding and the structural changes required to accommodate catecholamine agonists. Amino acids known to regulate receptor function are linked through packing interactions and a network of hydrogen bonds, suggesting a conformational pathway from the ligand-binding pocket to regions that interact with G proteins.

1,370 citations

Journal ArticleDOI
13 Jan 2011-Nature
TL;DR: A covalent agonist-bound β2AR–T4L fusion protein is designed that can be covalently tethered to a specific site on the receptor through a disulphide bond, and is capable of activating a heterotrimeric G protein.
Abstract: G-protein-coupled receptors (GPCRs) are eukaryotic integral membrane proteins that modulate biological function by initiating cellular signalling in response to chemically diverse agonists. Despite recent progress in the structural biology of GPCRs, the molecular basis for agonist binding and allosteric modulation of these proteins is poorly understood. Structural knowledge of agonist-bound states is essential for deciphering the mechanism of receptor activation, and for structure-guided design and optimization of ligands. However, the crystallization of agonist-bound GPCRs has been hampered by modest affinities and rapid off-rates of available agonists. Using the inactive structure of the human β(2) adrenergic receptor (β(2)AR) as a guide, we designed a β(2)AR agonist that can be covalently tethered to a specific site on the receptor through a disulphide bond. The covalent β(2)AR-agonist complex forms efficiently, and is capable of activating a heterotrimeric G protein. We crystallized a covalent agonist-bound β(2)AR-T4L fusion protein in lipid bilayers through the use of the lipidic mesophase method, and determined its structure at 3.5 A resolution. A comparison to the inactive structure and an antibody-stabilized active structure (companion paper) shows how binding events at both the extracellular and intracellular surfaces are required to stabilize an active conformation of the receptor. The structures are in agreement with long-timescale (up to 30 μs) molecular dynamics simulations showing that an agonist-bound active conformation spontaneously relaxes to an inactive-like conformation in the absence of a G protein or stabilizing antibody.

747 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
Hans Clevers1
03 Nov 2006-Cell
TL;DR: A remarkable interdisciplinary effort has unraveled the WNT (Wingless and INT-1) signal transduction cascade over the last two decades, finding that Germline mutations in the Wnt pathway cause several hereditary diseases, and somatic mutations are associated with cancer of the intestine and a variety of other tissues.

5,042 citations

Journal ArticleDOI
TL;DR: Some key aspects of Wnt/beta-catenin signaling in human diseases including congenital malformations, cancer, and osteoporosis are highlighted, and potential therapeutic implications are discussed.

4,926 citations

Journal ArticleDOI
01 Jan 2010-Science
TL;DR: The evidence for how this principle combines the potential for sphingolipid-cholesterol self-assembly with protein specificity to selectively focus membrane bioactivity is reviewed.
Abstract: Cell membranes display a tremendous complexity of lipids and proteins designed to perform the functions cells require. To coordinate these functions, the membrane is able to laterally segregate its constituents. This capability is based on dynamic liquid-liquid immiscibility and underlies the raft concept of membrane subcompartmentalization. Lipid rafts are fluctuating nanoscale assemblies of sphingolipid, cholesterol, and proteins that can be stabilized to coalesce, forming platforms that function in membrane signaling and trafficking. Here we review the evidence for how this principle combines the potential for sphingolipid-cholesterol self-assembly with protein specificity to selectively focus membrane bioactivity.

3,811 citations