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Receptor Structures

kidamnesiac

kidamnesiac

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Joined
Oct 19, 2006
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533
Have x-ray, or NMR (hell, I'll take neutron!), structures of any of the interesting neuroreceptors been determined? It seems everything I find is models based upon which compounds bind there, which is shite if you ax me.
If not, what the hell is so difficult? Hundreds of membrane bound receptors have been crystallized, I would think loads of post-docs in east coast medical uni labs would be setting up mountains of xtal trays for these things.
 
^^ They are pretty patterns that are a swine to interpret. Using x-rat diffraction patterns to determine 3D protein structure is like using the Ladybird book of atomic power as a manual for building a fast breeder reactor =D

They are pretty though (if you don't mind monochrome pictures)
 
Man, you people are on drugs
I'm going to take that as a no...not even a GABA or anything?
 
^^ hey i'm not that interested in receptor structures but yeah we are on drugs=D is that a problem for you lol :p:D
 
I think that most G-protein coupled receptors are too large for multidimensional NMR structural approaches. NMR works best for proteins under around 20 kDa. While X-ray crystallography doesn't have any size limitations, it is a real bitch. Each one of those pretty rendered proteins you see on the cover of Nature or Science magazine takes tens of thousands of hours of work to produce...and more than a lot of luck. Winning the lotto kind of luck. Getting things to crystalize is an art, not a science.

Also, nearly all crystal structures have been based upon bacterial homologues of mammalian proteins. Thus, I think the bacterial rhodopsin (and a transgenic version of bovine rhodopsin) are the only GPCRs that have been crystalized to date. Don't get me wrong though, I would love to see a 5-HT2A receptor with bound agonist (like DOI) crystalized.

As for the drugs: "you put on your headphones and step into the zone when you're on drugs...we are all on drugs, yeah--give me some of that stuff."
 
Last edited:
Hot off the press ...

Published Online October 25, 2007
Science DOI: 10.1126/science.1150577

http://www.sciencemag.org/cgi/content/abstract/1150577

High-Resolution Crystal Structure of an Engineered Human 2-Adrenergic G Protein–Coupled Receptor. Vadim Cherezov 1, Daniel M. Rosenbaum 2, Michael A. Hanson 1, Søren G. F. Rasmussen 3, Foon Sun Thian 3, Tong Sun Kobilka 3, Hee-Jung Choi 4, Peter Kuhn 5, William I. Weis 4, Brian K. Kobilka 3*, Raymond C. Stevens 1*

G protein–coupled receptors comprise the largest family of eukaryotic signal transduction proteins that communicate across the membrane. We report the crystal structure of a human 2-adrenergic receptor–T4 lysozyme fusion protein bound to the partial inverse agonist carazolol at 2.4 Å 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 2-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.
 
Dondante said:
Hot off the press ...

Published Online October 25, 2007
Science DOI: 10.1126/science.1150577

http://www.sciencemag.org/cgi/content/abstract/1150577

High-Resolution Crystal Structure of an Engineered Human 2-Adrenergic G Protein–Coupled Receptor. Vadim Cherezov 1, Daniel M. Rosenbaum 2, Michael A. Hanson 1, Søren G. F. Rasmussen 3, Foon Sun Thian 3, Tong Sun Kobilka 3, Hee-Jung Choi 4, Peter Kuhn 5, William I. Weis 4, Brian K. Kobilka 3*, Raymond C. Stevens 1*

G protein–coupled receptors comprise the largest family of eukaryotic signal transduction proteins that communicate across the membrane. We report the crystal structure of a human 2-adrenergic receptor–T4 lysozyme fusion protein bound to the partial inverse agonist carazolol at 2.4 Å 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 2-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.
Click to expand...

excellent, now all we need is a distributed project like SETI @ HOME to tap into the immense computing power available and use this model to hit the 5ht2a receptor...
I think the project should be called JUNKI @ HOME :)
 
There's one already called 'Folding@home", for the folding of proteins into enzymatic systems.
 
Good timing KidA! :D

It's being published in conjunction with the paper below. PM me with an email address if anybody wants the pdf.

GPCR Engineering Yields High-Resolution Structural Insights into 2 Adrenergic Receptor Function. Daniel M. Rosenbaum 1, Vadim Cherezov 2, Michael A. Hanson 2, Søren G. F. Rasmussen 1, Foon Sun Thian 1, Tong Sun Kobilka 1, Hee-Jung Choi 3, Xiao-Jie Yao 1, William I. Weis 3, Raymond C. Stevens 2*, Brian K. Kobilka 1*

The 2 adrenergic receptor (2AR) is a well-studied prototype for G protein-coupled receptors (GPCRs) that respond to diffusible hormones and neurotransmitters. To overcome the structural flexibility of the 2AR and to facilitate its crystallization, we engineered a 2AR fusion protein in which T4 Lysozyme replaces most of the third intracellular loop of the GPCR ("2AR-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 2AR-T4L provides insights into inverse agonist binding and 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.
 
@RZ-
I'm typing this from a crystallography lab, we work on small soluble proteins mostly, but when I see structures like photosystem 2, or >>500kd proteins, it makes me wonder why more receptors aren't available yet, when they are such valuable targets. There are some 15000 unique pdb structures, so it's not that unheard of to get xtals and have em diffract.

But yes, how bout that timing :)

hmm, i see it took scripps and stanford types to pull that one off

it's funny they mention that rhodopsin has a similar appearance but different binding pocket in the abstract-NO SHIT! if it had the same pocket we'd be kinda fucked eh?
 
hot off the presses, that shit was only submitted a month ago and its actually a prerelease, man im good
 
Thank you for the paper. My understanding is that the main problem is a crystallization problem. The amount of receptor protein is very small in biomaterials, and to achieve crystallization you need high purity. Also, membrane bound proteins are different than free protein. Crystallizing membrane proteins in active conformation is a different beast than crystallizing soluble proteins. There is however, much activity in this area.

We were fortunate enough to find Rhodopsin in extremely high concentration in a bacteria found in a muddy red pool of guck somewhere... ;)
 
recombinant technologies make most of this cake anymore
in fact, that is how the paper above was done, they actually engineered another protein into it to make it xtalizable
the problems arise from proper folding and shuttling of these types of proteins, but those things aren't usually huge stumbling blocks either, anymore anyway
 
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