Sandbox Reserved 1100: Difference between revisions

The Adiponectin receptor 1 contains <scene name='82/829353/7helices/1'>seven transmembrane helices</scene> linked thanks to three <scene name='82/829353/3externalloop/1'>extracellular loops</scene> and <scene name='82/829353/3internalloop/1'>three intracellular loops</scene>. The <scene name='82/829353/Helix1/2'>helix I</scene> is formed by the residues 135 to 157, <scene name='82/829353/Helix2/2'>helix II</scene> by the residues 169 to 192, the <scene name='82/829353/Helix3/2'>helix III</scene> by the residues 198 to 227, the <scene name='82/829353/Helix4/2'>helice IV</scene> by the residues 232 to 252, the <scene name='82/829353/Helice5/2'>helix V</scene> by the residues 264 to 288 <scene name='82/829353/Helix6/2'>heliX VI</scene> by the residues 305 to 319 and the <scene name='82/829353/Helix7/2'>helix VII</scene> by the residues 336 to 364 .Besides, the <scene name='82/829353/Helix3/2'>helix III</scene> and <scene name='82/829353/Helix7/2'>VII</scene> are longer than the other helices. These <scene name='82/829353/7tm/2'>seven transmembrane helices</scene> have a clockwise circular specific organisation (from helix I to helix VII) and form a bundle.  

Concerning the extracellular faces, the three <scene name='82/829353/3externalloop/1'>extracellular loops</scene> which connect the transmembrane helices are exposed and it is the same for the <scene name='82/829353/C-terminus_domain/3'>C-terminus domain</scene>. Besides, <scene name='82/829353/Helix3/2'>helix III</scene> and the <scene name='82/829353/Helix7/2'>VII</scene> are longer than the other helices and as a result the <scene name='82/829353/C-terminus_domain/3'>C-terminus domain</scene>  two turns of the <scene name='82/829353/Helix7/2'>VII</scene> are exposed too. <ref name="doc1"/>

In this cavity, there is a zinc ion which is coordinated thanks to three histidine residues. These three histidine residues are <scene name='82/829353/H191/2'>H191</scene> in the <scene name='82/829353/Helix2/2'>helix II</scene>, <scene name='82/829353/H337/2'>H337</scene> and <scene name='82/829353/H341/2'>H341</scene> in the <scene name='82/829353/Helix7/2'>helix VII</scene>. As a result, the zinc ion is in the intracellular layer of the membrane, in the neighbourhood of 4° deep from the inner surface of the plasma membrane. Thanks to its tetrahedral coordination, this zinc ion binds the <scene name='82/829353/Helix2/2'>helix II</scene>, <scene name='82/829353/Helix3/2'>III</scene> and <scene name='82/829353/Helix7/2'>VII</scene> together. The adiponectin-stimulated AMPK phosphorylation doesn’t directly require the zinc binding site, nevertheless it has been supposed that the zinc ion allows a stabilizing effect. <ref name="doc1"/>

AdipoR1 has the capacity to form [http://en.wikipedia.org/wiki/Oligomer oligomers]. <ref name="doc3"> Takashi Kadowaki and Toshimasa Yamauchi et al. « Adiponectin and adiponectin receptors». https://www.ncbi.nlm.nih.gov/pubmed/15897298</ref> Indeed in living cell both monomers and oligomers are present. A specific motif was identified to contribute to the AdipoR1 dimerization: it is the motif GxxxG in the transmembrane <scene name='82/829353/Helice5/2'>helix V</scene>. Besides, the dimerization of AdipoR1 is also regulated.  This dimerization is inhibited by the fixation of the full-length adiponectin while the globular adiponectin has any impact on the dimerization level of the AdipoR1 receptor. Thanks to mutant experiment, it can be supposed that the collagen-like domain of the full-length adiponectin is responsible to the dimer dissociation. There are strong evidences that dimerization of the AdipoR1 receptor has a role during the biosynthesis, the trafficking and the signalling of the seven transmembrane receptors. <ref name="doc4"> Kosel D, Heiker JT, Juhl C, Wottawah CM, Blüher M, Mörl K, Beck-Sickinger AG et al. « Dimerization of adiponectin 1 is inhibited by adiponectin » Journal of Cell Science 123, 1320-1328 (2010) : https://www.ncbi.nlm.nih.gov/pubmed/20332107</ref>