<h3>Title</h3>
<h3>Peptide Ligand G Protein-Coupled Receptors <span style="font-size: 12.16px;">are Dynamic Molecules in Lipid Membrane</span></h3>
<p><strong><span style="font-size: 12.16px;"><span style="text-decoration: underline;">Abstract</span> :</span></strong></p>
<p class="MsoNormal" style="text-align: justify;"><span style="font-size: 11.0pt;" lang="EN-US">G protein-coupled receptors (GPCRs) constitute a large group of membrane proteins, known to undergo a set of well-defined structural transitions upon activation and signaling. In our work, we address the molecular dynamics of peptide ligand GPCRs using solution and solid-state NMR. We work with human class A GPCRs that are activated by peptide hormones, such as neuropeptide Y (NPY) or ghrelin. The GPCRs are expressed in prokaryotic systems or by cell-free synthesis. In the talk, results on three research topics will be discussed. (<em>i</em>) Studies on the equilibrium dynamics of GPCRs using static <sup>15</sup>N CP NMR, <sup>15</sup>N NMR spectra acquired as a function of the CP contact time, and <sup>13</sup>C MAS NMR experiments confirm the high molecular dynamics of three peptide ligand GPCRs. Quantitative determination of <sup>1</sup>H-<sup>13</sup>C order parameters through measurement of the <sup>1</sup>H-<sup>13</sup>C dipolar couplings in separated local field NMR experiments revealed axially symmetric motions of the GPCRs and molecular fluctuations of large amplitude [1, 2]. (<em>ii</em>) </span><span style="font-size: 11.0pt; mso-ansi-language: EN-GB;" lang="EN-GB">Data will be reported that led to the development of structural models of NPY bound to the Y<sub>1</sub> and the </span><span style="font-size: 11.0pt;" lang="EN-US">Y<sub>2</sub> receptors</span><span style="font-size: 11.0pt; mso-ansi-language: EN-GB;" lang="EN-GB">. </span><span style="font-size: 11.0pt;" lang="EN-US">Isotope-labeled NPY was used to determine the secondary structure of the receptor bound ligand. Upon receptor binding, the C-terminal α‑helix of NPY, formed in membrane environment in the absence of receptor, is unwound starting at Thr<sup>32</sup> to make optimal contact of the C‑terminal residues within the binding pocket. The NMR signals of several hydrophobic residues in the α-helical region of NPY were broadened upon receptor binding. The ligands are tethered to the second extracellular loop by hydrophobic contacts, with the N-terminal part of its helix facing the solvent. The C‑terminal pentapeptide of NPY inserts deeply into the transmembrane bundle, making optimal contacts to the Y<sub>2</sub> receptor including a contact NPY’s amidated C‑terminus with Gln<sup>3.32</sup> in a polar cluster within helices 2 and 3 of the receptor [3, 4]. (<em>iii</em>) We will report data on the dynamics and ligand binding of the human GHS receptor, which plays a key role in the development of obesity [5]. </span></p>
<p class="MsoNormal"><span style="font-size: 11.0pt;" lang="EN-US"> </span></p>
<p class="References"><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-ansi-language: DE;" lang="DE">[1]</span><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-ansi-language: DE;" lang="DE">Schmidt et al. <em>Chemistry</em> <strong>2014</strong>, 20, 4986.</span></p>
<p class="References"><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-ansi-language: DE;" lang="DE">[2] Thomas et al. <em>J. Biomol. NMR</em> <strong>2015</strong>, 61, 347.</span></p>
<p class="References"><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-ansi-language: DE;" lang="DE">[3] Kaiser et al. <em>Angew. </em></span><em><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-ansi-language: EN-US;" lang="EN-US">Chem. Int. Ed.</span></em><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-ansi-language: EN-US;" lang="EN-US"> <strong>2015</strong>, 52, </span><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif';" lang="FR">7446.</span></p>
<p class="References"><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif';" lang="FR">[4] </span><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: Batang;" lang="FR">Yang et al. <em>Nature</em> <strong>2018</strong>, DOI: 10.1038/s41586-018-0046-x, <em>in press</em>.</span></p>
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<p class="References"><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif';" lang="FR">[5] Schrottke et al. </span><em><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-ansi-language: EN-US;" lang="EN-US">Sci. Rep.</span></em><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-ansi-language: EN-US;" lang="EN-US"> <strong>2017</strong>, 7, 46128.</span></p>
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