Gpcr structures 061213b


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Gpcr structures 061213b

  1. 1. Structural studies of GPCRs Tony Harmar University of Edinburgh
  2. 2. Structure of the first membrane protein The first membrane protein that was structurally characterised, by RichardHenderson (left) and Nigel Unwin (right) in 1975, was bacteriorhodopsin, a light-harvesting membrane protein from the archaean Halobacterium halobium that acts as a lightdriven proton pump and is the only protein constituent of the purple membrane, a two-dimensional crystal lattice naturally present as part of the plasma membrane of the bacterium.
  3. 3. Bacteriorhodopsin -the first 7TM protein Using electron diffraction, Henderson & Unwin showed that the protein contains seven alpha-helices that enclose an all-trans retinal chromophore that undergoes an isomerisation process upon light absorption that results in the translocation of a proton from the cytoplasmic side to the extracellular side of the membrane.They commented, almost prophetically“The purple membrane thus seems to provide a simple example of an 'intrinsic' membrane protein, a class of structure to which many molecular pumps and channels must belong. We would not be surprised if the simple arrangement of helices found here also occurs in some of these other intrinsic membrane proteins”
  4. 4. Amino acid sequence of bacteriorhodopsin The amino acid sequence of bacteriorhodopsin was first published, almost simultaneously, by the groups of Yuri Ovchinnikov in 1978 and Nobel Laureate Har Gobind Khorana in1979. Each study represented a tour de force of protein chemistry.
  5. 5. The first depiction of the 7TM topology of bacteriorhodopsin, from Ovchinnikov.
  6. 6. Amino acid sequence of the first GPCR 1983: Complete amino acid sequence of bovine rhodopsin determined by the laboratories of Ovchinnikov (Russia) and Hargrave (USA.
  7. 7. First cDNA and gene sequences 1983:cloning of cDNA and gene encoding bovine rhodopsin by Jeremy Nathans (left) and David Hogness (right). Using a “citation classic” technique for homology screening devised by Hogness, they later identified three related visual pigment
  8. 8. 1986:Cloning of β2 adrenoceptor – the first nonsensory GPCR
  9. 9. 1986:Cloning of β2 adrenoceptor – the first nonsensory GPCR
  10. 10. Cloning the β 2 adrenoceptor • Receptor from hamster lung solubilised in detergent and purified by affinity chromatography on alprenolol-sepharose • Progress of purification monitored by binding of [ 125 I]-cyanopindolol • Attempts to obtain amino acid sequence of the intact protein failed • Purified protein was subjected to chemical cleavage with cyanogen bromide (CNBr), which cleaves proteins after every methionine residue • Cyanogen bromide fragments were purified by HPLC and sequenced
  11. 11. Cloning the β 2 adrenoceptor
  12. 12. Cloning the β 2 adrenoceptor
  13. 13. 1988:the first "orphan" GPCR Nature 335: 358-360 (1988) G-21 was a genomic clone with homology to the β2AR: at first its endogenous ligand was unknown, i.e. it encoded an “orphan” GPCR Nature 335: 358-360 (1988)
  14. 14. 1988:5-HT1A receptor “deorphanised” When expressed in cell lines and studied in a radioligand binding assay, G-21 exhibited the pharmacology of the 5HT1A receptor
  15. 15. 1987:Expression cloning of the NK2 receptor, the first peptide GPCR 1987:cDNA sequence encoding the the NK2 receptor was reported by the group of Shigetada Nakanishi using an ingenious expression cloning strategy
  16. 16. Cloning the NK 2 receptor by expression in Xenopus oocytes 1987:pools of mRNA transcripts from bovine stomach cDNAwere injected into Xenopus oocytes and tested for electrophysiological responses to neurokinin A. Pools were progressively subdivided until a single responsive
  17. 17. 1991:Expression cloning of the metabotropic glutamate receptor mGlu1, the first GPCR from Class C 1991:The cDNA sequence was also cloned by Nakanishi’s group via screening of RNA transcripts in Xenopus oocytes. Picture shows mRNA distribution in hippocampus by in situ hybridisation
  18. 18. 1991:Expression cloning of the secretin receptor, the first Class B GPCR 1991:The secretin receptor was cloned by the laboratory of Shigekazu Nagata by expression in COS cells
  19. 19. 1991:Crystal structure of rhodopsin 1991:Crystal structure of rhodopsin determined by Krzysztof Palczewski and colleagues (click to play movie)
  20. 20. 2003- Datamining 1991:Whole genome sequencing prompted searches for the full mammalian complement of GPCRs and phylogenetic analysis
  21. 21. 2007:Crystal structure of the β2 adrenoceptor 2007:the first high-resolution structure of a GPCR. Crystal structure was determined by the labs of Brian Kobilka and Ray Stevens. Science cover caption reads”Structure of the human β2-adrenergic receptor (red) embedded in a lipid membrane and bound to a diffusible ligand (green), with cholesterol (yellow) between the two receptor molecules. A cartoon of the lipidic cubic phase used for crystallization of the receptor is shown in the background”
  22. 22. Activated human β2 adrenergic receptor (in blue ) in a complex with a heterotrimeric G protein (3 subunits:reddish to orange-brown) and hormone (gold), resolution 3.2Å. The boundaries of the membrane in which the GPCR sits are represented in light green. From Proteopedia (click to play movie).
  23. 23. Activated human β2 adrenergic receptor (in blue ) in a complex with a heterotrimeric G protein (3 subunits:reddish to orange-brown) and hormone (gold), resolution 3.2Å. The boundaries of the membrane in which the GPCR sits are represented in light green. From Proteopedia (click to play movie).
  24. 24. 2012:Nobel Prize in Chemistry Awarded to Robert Lefkowitz (left)and Brian Kobilka (right) "for studies of G-protein-coupled receptors"