Glucagon amyloid-like fibril morphology is selected via morphology-dependent growth inhibition
Glucagon amyloid-like fibril morphology is selected via morphology-dependent growth inhibition
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DOI：
10.1021/bi6025374
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发表时间：
2007-06-19
期刊：
影响因子：
2.9
通讯作者：
Rischel, Christian
中科院分区：
文献类型：
--
作者：
Andersen, Christian Beyschau;Otzen, Daniel;Rischel, Christian
29个残基的肽激素胰高血糖素在低pH下容易原纤维化，但原纤维的结构和形态对环境条件非常敏感。在这里，我们研究了在不同肽浓度下形成胰高血糖素原纤维时观察到的形态差异背后的机制。电子显微镜显示在低胰高血糖素浓度（0.25 mg/mL）下形成的原纤维是扭曲的，而在高浓度（8 mg/mL）下形成的原纤维是直的。监测不同浓度下的原纤化动力学，我们发现滞后时间在1 mg/mL的浓度下具有意想不到的最大值，在较低和较高浓度下都具有更快的原纤化。接种实验表明，少量的直原纤维种子可以在低和高胰高血糖素浓度下加速原纤维生长，而扭曲的原纤维种子不能在高浓度下生长。我们的结论是，存在一种形态依赖性的机制，抑制胰高血糖素纤维的生长。光散射实验表明，胰高血糖素在低于1 mg/mL时主要是单体，而在高于该浓度时则越来越多地是三聚体。我们提出胰高血糖素三聚体能够特异性抑制扭曲原纤维形态的生长。这种抑制性结合的分子在一个非生产性的构象也可以发挥作用，在选择形态的其他原纤维形成肽和蛋白质。
The 29-residue peptide hormone glucagon readily fibrillates at low pH, but the structure and morphology of the fibrils are very sensitive to the environmental conditions. Here we have investigated the mechanism behind the differences in morphology observed when glucagon fibrils are formed at different peptide concentrations. Electron microscopy shows that fibrils formed at low glucagon concentration (0.25 mg/mL) are twisted, while fibrils formed at high concentration (8 mg/mL) are straight. Monitoring the fibrillation kinetics at different concentrations, we find that the lag time has an unexpected maximum at a concentration of 1 mg/mL, with faster fibrillation at both lower and higher concentrations. Seeding experiments show that small amounts of straight fibril seeds can accelerate fibril growth at both low and high glucagon concentration, while twisted fibril seeds cannot grow at high concentrations. We conclude that there exists a morphology-dependent mechanism for inhibition of glucagon fibril growth. Light scattering experiments indicate that glucagon is mainly monomeric below 1 mg/mL and increasingly trimeric above this concentration. We propose that the glucagon trimer is able to specifically inhibit growth of the twisted fibril morphology. Such inhibitory binding of molecules in an unproductive conformation could also play a role in the selection of morphologies for other fibril-forming peptides and proteins.