High-Resolution Crystal Structure of an Engineered Human β2-Adrenergic G Protein–Coupled Receptor
23 Nov 2007-Science (American Association for the Advancement of Science)-Vol. 318, Iss: 5854, pp 1258-1265
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.
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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
TL;DR: G-protein-coupled receptors mediate most of the authors' physiological responses to hormones, neurotransmitters and environmental stimulants, and so have great potential as therapeutic targets for a broad spectrum of diseases.
Abstract: G-protein-coupled receptors (GPCRs) mediate most of our physiological responses to hormones, neurotransmitters and environmental stimulants, and so have great potential as therapeutic targets for a broad spectrum of diseases. They are also fascinating molecules from the perspective of membrane-protein structure and biology. Great progress has been made over the past three decades in understanding diverse GPCRs, from pharmacology to functional characterization in vivo. Recent high-resolution structural studies have provided insights into the molecular mechanisms of GPCR activation and constitutive activity.
1,965 citations
TL;DR: This paper presents a new approach to drug design called “combinatorial biosynthesis and drug discovery through nanofiltration”, which combines the efforts of a single investigator with those of a number of other scientists.
Abstract: Multicomponent reactions (MCRs) are one-pot reactions employing more than two starting materials, e.g. 3, 4, … 7, where most of the atoms of the starting materials are incorporated in the final product.1 Several descriptive tags are regularly attached to MCRs (Fig. 1): they are atom economic, e.g. the majority if not all of the atoms of the starting materials are incorporated in the product; they are efficient, e.g. they efficiently yield the product since the product is formed in one-step instead of multiple sequential steps; they are convergent, e.g. several starting materials combine in one reaction to form the product; they exhibit a very high bond-forming-index (BFI), e.g. several non-hydrogen atom bonds are formed in one synthetic transformation.2 Therefore MCRs are often a useful alternative to sequential multistep synthesis.
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Figure 1
Above: multistep syntheses can be divergent (sequential) or convergent; below: in analogy MCR reactions are convergent and one or two component reactions are divergent or less convergent.
1,840 citations
TL;DR: The crystal structure of the human A2A adenosine receptor is determined, in complex with a high-affinity subtype-selective antagonist, ZM241385, to 2.6 angstrom resolution and suggests a role for ZM 241385 in restricting the movement of a tryptophan residue important in the activation mechanism of the class A receptors.
Abstract: The adenosine class of heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) mediates the important role of extracellular adenosine in many physiological processes and is antagonized by caffeine. We have determined the crystal structure of the human A2A adenosine receptor, in complex with a high-affinity subtype-selective antagonist, ZM241385, to 2.6 angstrom resolution. Four disulfide bridges in the extracellular domain, combined with a subtle repacking of the transmembrane helices relative to the adrenergic and rhodopsin receptor structures, define a pocket distinct from that of other structurally determined GPCRs. The arrangement allows for the binding of the antagonist in an extended conformation, perpendicular to the membrane plane. The binding site highlights an integral role for the extracellular loops, together with the helical core, in ligand recognition by this class of GPCRs and suggests a role for ZM241385 in restricting the movement of a tryptophan residue important in the activation mechanism of the class A receptors.
1,754 citations
TL;DR: Five independent crystal structures of CXCR4 bound to an antagonist small molecule IT1t and a cyclic peptide CVX15 at 2.5 to 3.2 angstrom resolution reveal a consistent homodimer with an interface including helices V and VI that may be involved in regulating signaling.
Abstract: Chemokine receptors are critical regulators of cell migration in the context of immune surveillance, inflammation, and development. The G protein-coupled chemokine receptor CXCR4 is specifically implicated in cancer metastasis and HIV-1 infection. Here we report five independent crystal structures of CXCR4 bound to an antagonist small molecule IT1t and a cyclic peptide CVX15 at 2.5 to 3.2 angstrom resolution. All structures reveal a consistent homodimer with an interface including helices V and VI that may be involved in regulating signaling. The location and shape of the ligand-binding sites differ from other G protein-coupled receptors and are closer to the extracellular surface. These structures provide new clues about the interactions between CXCR4 and its natural ligand CXCL12, and with the HIV-1 glycoprotein gp120.
1,682 citations
References
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TL;DR: The application of numerical methods are presented to enable the trivially parallel solution of the Poisson-Boltzmann equation for supramolecular structures that are orders of magnitude larger in size.
Abstract: Evaluation of the electrostatic properties of biomolecules has become a standard practice in molecular biophysics. Foremost among the models used to elucidate the electrostatic potential is the Poisson-Boltzmann equation; however, existing methods for solving this equation have limited the scope of accurate electrostatic calculations to relatively small biomolecular systems. Here we present the application of numerical methods to enable the trivially parallel solution of the Poisson-Boltzmann equation for supramolecular structures that are orders of magnitude larger in size. As a demonstration of this methodology, electrostatic potentials have been calculated for large microtubule and ribosome structures. The results point to the likely role of electrostatics in a variety of activities of these structures.
6,918 citations
TL;DR: This article determined the structure of rhodopsin from diffraction data extending to 2.8 angstroms resolution and found that the highly organized structure in the extracellular region, including a conserved disulfide bridge, forms a basis for the arrangement of the sevenhelix transmembrane motif.
Abstract: Heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) respond to a variety of different external stimuli and activate G proteins. GPCRs share many structural features, including a bundle of seven transmembrane alpha helices connected by six loops of varying lengths. We determined the structure of rhodopsin from diffraction data extending to 2.8 angstroms resolution. The highly organized structure in the extracellular region, including a conserved disulfide bridge, forms a basis for the arrangement of the seven-helix transmembrane motif. The ground-state chromophore, 11-cis-retinal, holds the transmembrane region of the protein in the inactive conformation. Interactions of the chromophore with a cluster of key residues determine the wavelength of the maximum absorption. Changes in these interactions among rhodopsins facilitate color discrimination. Identification of a set of residues that mediate interactions between the transmembrane helices and the cytoplasmic surface, where G-protein activation occurs, also suggests a possible structural change upon photoactivation.
5,357 citations
TL;DR: This study represents the first overall map of the GPCR sequences in a single mammalian genome and shows several common structural features indicating that the human GPCRs in the GRAFS families share a common ancestor.
Abstract: The superfamily of G-protein-coupled receptors (GPCRs) is very diverse in structure and function and its members are among the most pursued targets for drug development. We identified more than 800 human GPCR sequences and simultaneously analyzed 342 unique functional nonolfactory human GPCR sequences with phylogenetic analyses. Our results show, with high bootstrap support, five main families, named glutamate, rhodopsin, adhesion, frizzled/taste2, and secretin, forming the GRAFS classification system. The rhodopsin family is the largest and forms four main groups with 13 sub-branches. Positions of the GPCRs in chromosomal paralogons regions indicate the importance of tetraploidizations or local gene duplication events for their creation. We also searched for "fingerprint" motifs using Hidden Markov Models delineating the putative inter-relationship of the GRAFS families. We show several common structural features indicating that the human GPCRs in the GRAFS families share a common ancestor. This study represents the first overall map of the GPCRs in a single mammalian genome. Our novel approach of analyzing such large and diverse sequence sets may be useful for studies on GPCRs in other genomes and divergent protein families.
2,677 citations
TL;DR: The biotech industry is establishing itself as the discovery arm of the pharmaceutical industry, and in bridging the gap between academia and large pharmaceutical companies, the biotech firms have been effective instruments of technology transfer.
Abstract: Driven by chemistry but increasingly guided by pharmacology and the clinical sciences, drug research has contributed more to the progress of medicine during the past century than any other scientific factor. The advent of molecular biology and, in particular, of genomic sciences is having a deep impact on drug discovery. Recombinant proteins and monoclonal antibodies have greatly enriched our therapeutic armamentarium. Genome sciences, combined with bioinformatic tools, allow us to dissect the genetic basis of multifactorial diseases and to determine the most suitable points of attack for future medicines, thereby increasing the number of treatment options. The dramatic increase in the complexity of drug research is enforcing changes in the institutional basis of this interdisciplinary endeavor. The biotech industry is establishing itself as the discovery arm of the pharmaceutical industry. In bridging the gap between academia and large pharmaceutical companies, the biotech firms have been effective instruments of technology transfer.
2,551 citations