title: Integrating solid-state NMR and computational modeling to investigate the structure and dynamics of membrane-associated ghrelin.
abstract: The peptide hormone ghrelin activates the growth hormone secretagogue receptor 1a, also known as the ghrelin receptor. This 28-residue peptide is acylated at Ser3 and is the only peptide hormone in the human body that is lipid-modified by an octanoyl group. Little is known about the structure and dynamics of membrane-associated ghrelin. We carried out solid-state NMR studies of ghrelin in lipid vesicles, followed by computational modeling of the peptide using Rosetta. Isotropic chemical shift data of isotopically labeled ghrelin provide information about the peptide's secondary structure. Spin diffusion experiments indicate that ghrelin binds to membranes via its lipidated Ser3. Further, Phe4, as well as electrostatics involving the peptide's positively charged residues and lipid polar headgroups, contribute to the binding energy. Other than the lipid anchor, ghrelin is highly flexible and mobile at the membrane surface. This observation is supported by our predicted model ensemble, which is in good agreement with experimentally determined chemical shifts. In the final ensemble of models, residues 8-17 form an α-helix, while residues 21-23 and 26-27 often adopt a polyproline II helical conformation. These helices appear to assist the peptide in forming an amphipathic conformation so that it can bind to the membrane.
authors: Institute of Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany.
authors: Gerrit
authors: G
authors: Vortmeier
authors: Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, 37232, United States of America.
authors: Stephanie H
authors: SH
authors: DeLuca
authors: Institute of Biochemistry, University of Leipzig, Leipzig, Germany.
authors: Sylvia
authors: S
authors: Els-Heindl
authors: Institute of Biochemistry, University of Leipzig, Leipzig, Germany.
authors: Constance
authors: C
authors: Chollet
authors: Institute of Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany.
authors: Holger A
authors: HA
authors: Scheidt
authors: Institute of Biochemistry, University of Leipzig, Leipzig, Germany.
authors: Annette G
authors: AG
authors: Beck-Sickinger
authors: Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, 37232, United States of America.
authors: Jens
authors: J
authors: Meiler
authors: Institute of Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany.
authors: Daniel
authors: D
authors: Huster
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D019295:Computational Biology / Q000379:methods*; D054439:Ghrelin / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation
chemical_list: D054439:Ghrelin