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== G-Protein Activation Cycle ==
== G-Protein Activation Cycle ==
[[Image:Img.JPG|600px|G protein cycle for the β2AR–Gs complex. Reprinted by permission from Macmillan Publishers Ltd on behalf of Cancer Research UK: Nature 477, 549–555, copyright 2011]]
[[Image:Img.JPG|400px|G protein cycle for the β2AR–Gs complex. Reprinted by permission from Macmillan Publishers Ltd on behalf of Cancer Research UK: Nature 477, 549–555, copyright 2011]]


The figure shows the G Protein cycle<ref>doi:10.1038/nature10361</ref> - an extracellular agonist binding to the β2AR leads to <scene name='70/701430/Receptor_morphing_animation/2'>conformational rearrangements</scene> of the cytoplasmic ends of transmembrane segments that enable the Gs heterotrimer to bind the receptor. GDP is released from the α subunit upon formation of β2AR–Gs complex. The GTP binds to the nucleotide-free α subunit resulting in dissociation of the α and βγ subunits from the receptor. The subunits regulate their respective effector proteins adenylyl cyclase (AC) and Ca2+ channels. The Gs heterotrimer reassembles from α and βγ subunits following hydrolysis of GTP to GDP in the α subunit.  
The figure shows the G Protein cycle<ref>doi:10.1038/nature10361</ref> - an extracellular agonist binding to the β2AR leads to <scene name='70/701430/Receptor_morphing_animation/2'>conformational rearrangements</scene> of the cytoplasmic ends of transmembrane segments that enable the Gs heterotrimer to bind the receptor. GDP is released from the α subunit upon formation of β2AR–Gs complex. The GTP binds to the nucleotide-free α subunit resulting in dissociation of the α and βγ subunits from the receptor. The subunits regulate their respective effector proteins adenylyl cyclase (AC) and Ca2+ channels. The Gs heterotrimer reassembles from α and βγ subunits following hydrolysis of GTP to GDP in the α subunit.  


{{Template:Button Toggle Animation2}}  
{{Template:Button Toggle Animation2}}


== G-Protein variability ==
 
The Gαs subunit consists of two domains, the <scene name='70/701430/Alpharas/2'>Ras domain (GαsRas)</scene> and the <scene name='70/701430/Alphahelical/2'>α-helical domain (GαsAH)</scene>. A previous structure of a GTPγS bound (i.e. active, "turned on") Gαs protein (PDB ID: [http://www.rcsb.org/pdb/explore/explore.do?structureId=1AZT 1AZT]) showed that both domains are involved in nucleotide binding, as the nucleotide-binding pocket of the Gαs subunit is formed by the interface between GαsRas and GαsAH<ref>doi:10.1126/science.278.5345.1943</ref>. It was also previously known that the GsαAH domain has a variable position relative to the GsαRas domain between this GTP bound (active) state and the nucleotide free state<ref>DOI:10.1126/science.8266082</ref><ref>doi:10.1073/pnas.1105810108</ref><ref>doi:10.1073/pnas.1113645108</ref><ref>doi:10.1038/nature10488</ref>. However, the β2AR–Gs complex structure of the receptor attached to the empty (no guanosine phosphate attached) G protein enabled comparing it to the active (GTP bound) structure and by that showing <scene name='70/701430/Gamorph/2'>how large this displacement is</scene> - this is probably the most surprising observation arising from the β2AR–Gs complex.
==See Also==
*[[Adrenergic receptor|Adrenergic receptor]]
*[[Antibody|Antibody]]
*[[Beta-2 Adrenergic Receptor|Beta-2 Adrenergic Receptor]]
*[[G protein-coupled receptor|G protein-coupled receptor]]
*[[GTP-binding protein|GTP-binding protein]]
*[[Guanine nucleotide-binding protein|Guanine nucleotide-binding protein]]
*[[Hormone|Hormone]]
*[[Lysozyme 3D structures|Lysozyme 3D structures]]
*[[Nobel Prizes for 3D Molecular Structure|Nobel Prizes for 3D Molecular Structure]]
*[[Suggestions for new articles|Suggestions for new articles]]
*[[Transducin|Transducin]]
*[[User:Wayne Decatur/UNH BCHEM833 Structural Analysis Workshop Session Fall 2012|User:Wayne Decatur/UNH BCHEM833 Structural Analysis Workshop Session Fall 2012]]
*[[User:Wayne Decatur/UNH BCHEM833 Structural Proteomics Introductory Lecture Fall 2012|User:Wayne Decatur/UNH BCHEM833 Structural Proteomics Introductory Lecture Fall 2012]]
*[[3sn6|3SN6]]
</StructureSection>
== References ==
<references/>
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