Roles of specific extracellular domains of the glucagon receptor in ligand binding and signaling.
Roles of specific extracellular domains of the glucagon receptor in ligand binding and signaling.
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DOI：
10.1021/bi025711j
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发表时间：
2002-09
期刊：
影响因子：
2.9
通讯作者：
C. Unson;Cui-Rong Wu;Youwei Jiang;B. Yoo;Connie P. Cheung;T. Sakmar;R. B. Merrifield
中科院分区：
文献类型：
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作者：
C. Unson;Cui-Rong Wu;Youwei Jiang;B. Yoo;Connie P. Cheung;T. Sakmar;R. B. Merrifield
为了鉴定胰升糖素受体中配体结合的结构决定因素，我们制备了8个受体嵌合体和附加的受体点突变体。细胞外N端的103-117和126-137个氨基酸残基和第一个细胞外环的206-219和220-231位残基被相应的胰升糖素样肽-1受体或促胰液素受体片段所取代。激素结合需要胰升糖素受体N端尾部和第一细胞外环的特定片段。第一个环的206-219片段似乎对胰升糖素结合和受体激活都很重要。对由胰高血糖素的N端14个残基和胰升糖素样肽1的C端17个残基组成的合成嵌合肽的功能研究表明，激素结合特异性可能涉及第一环的这一段。结合选择性可能部分来自该片段中的天冬氨酸残基。位于第二跨膜螺旋和第一环连接处的R-202突变导致突变的受体无法结合胰高血糖素或信号。我们的结论是，高亲和力的胰升糖素结合需要与胰升糖素受体N端尾部和第一细胞外环区的残基多次接触，激素特异性主要来自于206-219氨基酸片段。这些数据提出了一种模型，在该模型中，胰高血糖素首先与受体的N-末端结构域相互作用，然后在多肽的N-末端半部分与受体的第一个细胞外环之间进行更具体的相互作用，从而导致激活。
To identify structural determinants of ligand binding in the glucagon receptor, eight receptor chimeras and additional receptor point mutants were prepared and studied. Amino acid residues 103-117 and 126-137 in the extracellular N-terminal tail and residues 206-219 and 220-231 in the first extracellular loop of the glucagon receptor were replaced with the corresponding segments of the glucagon-like peptide-1 receptor or the secretin receptor. Specific segments of both the N-terminal tail and the first extracellular loop of the glucagon receptor are required for hormone binding. The 206-219 segment of the first loop appears to be important for both glucagon binding and receptor activation. Functional studies with a synthetic chimeric peptide consisting of the N-terminal 14 residues of glucagon and the C-terminal 17 residues of glucagon-like peptide 1 suggest that hormone binding specificity may involve this segment of the first loop. The binding selectivity may arise in part from aspartic acid residues in this segment. Mutation of R-202 located at the junction between the second transmembrane helix and the first loop resulted in a mutant receptor that failed to bind glucagon or signal. We conclude that high-affinity glucagon binding requires multiple contacts with residues in the N-terminal tail and first extracellular loop domain of the glucagon receptor, with hormone specificity arising primarily from the amino acid 206-219 segment. The data suggest a model whereby glucagon first interacts with the N-terminal domain of the receptor followed by more specific interactions between the N-terminal half of the peptide and the first extracellular loop of the receptor, leading to activation.