Sandbox Reserved 1167: Difference between revisions

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However, one particular difference between class A receptors and class B receptors is an inward shift of the intracellular component of Helix VII. In class A receptors this inward shift is instrumental in receptor activation, yet in class B receptors it remains unclear what role this shift plays<ref name ='structure_article'>PMID:23863937</ref>.  
However, one particular difference between class A receptors and class B receptors is an inward shift of the intracellular component of Helix VII. In class A receptors this inward shift is instrumental in receptor activation, yet in class B receptors it remains unclear what role this shift plays<ref name ='structure_article'>PMID:23863937</ref>.  
    
    
In contrast to class A glucagon receptors which have a [https://en.wikipedia.org/wiki/Proline proline] kink, in all  [https://en.wikipedia.org/wiki/Secretin_receptor_family secretin-like class B glucagon receptors] a [https://en.wikipedia.org/wiki/Glycine Glycine] at position 393 in Helix VII allows for a <scene name='72/721537/Gly_393_helical_bend/1'>helical bend</scene>. This glycine helical bend is fully [https://en.wikipedia.org/wiki/Conserved_sequence conserved] in all secretin-like class B receptors.
In contrast to class A glucagon receptors which have a [https://en.wikipedia.org/wiki/Proline proline] kink, in all  [https://en.wikipedia.org/wiki/Secretin_receptor_family secretin-like class B glucagon receptors] a [https://en.wikipedia.org/wiki/Glycine Glycine] at position 393 in Helix VII allows for a <scene name='72/721537/Gly_393_helical_bend/3'>helical bend</scene>. This glycine helical bend is fully [https://en.wikipedia.org/wiki/Conserved_sequence conserved] in all secretin-like class B receptors.


Another important structural component found in all secretin-like class B receptors are the two conserved [https://en.wikipedia.org/wiki/Salt_bridge_%28protein_and_supramolecular%29 salt bridges] found between [https://en.wikipedia.org/wiki/Arginine Arg] 346 and [https://en.wikipedia.org/wiki/Glutamic_acid Glu] 406 and Arg 173 and Glu 406 [[Image:Salt Bridge Interactions.png | 250 px|right|thumb|Glu 406 Salt Bridges]]. These salt bridges are a distinct feature of class B receptors because their interaction results in the distinct stalk found only in class B receptors<ref name ='structure_article'>PMID:23863937</ref>.   
Another important structural component found in all secretin-like class B receptors are the two conserved [https://en.wikipedia.org/wiki/Salt_bridge_%28protein_and_supramolecular%29 salt bridges] found between [https://en.wikipedia.org/wiki/Arginine Arg] 346 and [https://en.wikipedia.org/wiki/Glutamic_acid Glu] 406 and Arg 173 and Glu 406. These <scene name='72/721537/Salt_bridges/2'>salt bridges</scene> are a distinct feature of class B receptors because their interaction results in the distinct stalk found only in class B receptors<ref name ='structure_article'>PMID:23863937</ref>.   


While interface interactions between helices VI, V, and III, are not unique to class B receptors because certain homologous residues exist in class A receptors (like [https://en.wikipedia.org/wiki/Tyrosine Tyr] 239 and Leu 358), as a part of the interface <scene name='72/721537/Helical_interactions_vi-v-iii/2'>stabilization</scene> between helices VI, V, and III, a Class B-specific [https://en.wikipedia.org/wiki/Hydrogen_bond hydrogen bond] occurs between [https://en.wikipedia.org/wiki/Asparagine Asn] 318 of Helix V and [https://en.wikipedia.org/wiki/Leucine Leu] 242 of Helix III <ref name ='structure_article'>PMID:23863937</ref>.  
While interface interactions between helices VI, V, and III, are not unique to class B receptors because certain homologous and even conserved residues exist in class A receptors (like [https://en.wikipedia.org/wiki/Tyrosine Tyr] 239 and Leu 358), as a part of the interface <scene name='72/721537/Helical_interactions_vi-v-iii/2'>stabilization</scene> between helices VI, V, and III, a Class B-specific [https://en.wikipedia.org/wiki/Hydrogen_bond hydrogen bond] occurs between [https://en.wikipedia.org/wiki/Asparagine Asn] 318 of Helix V and [https://en.wikipedia.org/wiki/Leucine Leu] 242 of Helix III <ref name ='structure_article'>PMID:23863937</ref>.  


=== GCGR-Specific Traits ===
=== GCGR-Specific Traits ===
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====Other Unique Structural Features ====
====Other Unique Structural Features ====


An important interface stabilization interaction between Helices I and VII occurs between [https://en.wikipedia.org/wiki/Serine Ser] 152 of Helix I and Ser 390 of Helix VII. Due to their close proximity to one another, they form an important <scene name='72/721537/Ser-ser_hydrogen_bond/2'>hydrogen bond</scene> which stabilizes the structure of GCGR. Mutations to the homologous residues Ser 135 and Ser 392 have been shown to alter receptor signaling in [https://en.wikipedia.org/wiki/Glucagon-like_peptide_1_receptor glucagon-like peptide-1 receptor] (GLP1R).   
An important interface stabilization interaction between Helices I and VII occurs between [https://en.wikipedia.org/wiki/Serine Ser] 152 of Helix I and Ser 390 of Helix VII. Due to their close proximity to one another, they form an important <scene name='72/721537/Ser-ser_hydrogen_bond/3'>hydrogen bond</scene> which stabilizes the structure of GCGR. Mutations to the homologous residues Ser 135 and Ser 392 have been shown to alter receptor signaling in [https://en.wikipedia.org/wiki/Glucagon-like_peptide_1_receptor glucagon-like peptide-1 receptor] (GLP1R).