Vortmeier Gerrit, DeLuca Stephanie H, Els-Heindl Sylvia, Chollet Constance, Scheidt Holger A, Beck-Sickinger Annette G, Meiler Jens, Huster Daniel
Institute of Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany.
Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, 37232, United States of America.
PLoS One. 2015 Mar 24;10(3):e0122444. doi: 10.1371/journal.pone.0122444. eCollection 2015.
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.
肽激素胃饥饿素可激活生长激素促分泌素受体1a，也称为胃饥饿素受体。这种由28个氨基酸残基组成的肽在丝氨酸3处被酰化，是人体中唯一通过辛酰基进行脂质修饰的肽激素。目前对与膜相关的胃饥饿素的结构和动力学了解甚少。我们对脂质囊泡中的胃饥饿素进行了固态核磁共振研究，随后使用Rosetta对该肽进行了计算建模。同位素标记的胃饥饿素的各向同性化学位移数据提供了有关该肽二级结构的信息。自旋扩散实验表明，胃饥饿素通过其脂质化的丝氨酸3与膜结合。此外，苯丙氨酸4以及涉及该肽带正电荷残基和脂质极性头部基团的静电作用对结合能有贡献。除了脂质锚定基团外，胃饥饿素在膜表面具有高度的灵活性和流动性。我们预测的模型集支持了这一观察结果，该模型集与实验测定的化学位移非常吻合。在最终的模型集中，残基8 - 17形成一个α螺旋，而残基21 - 23和26 - 27通常采用多聚脯氨酸II螺旋构象。这些螺旋似乎有助于该肽形成两亲性构象，从而使其能够与膜结合。
