Ministry of Education Key Laboratory of Carbohydrate Chemistry and Biotechnology, School of Biotechnology, Jiangnan University, Wuxi, China.
Ministry of Education Key Laboratory of Carbohydrate Chemistry and Biotechnology, School of Biotechnology, Jiangnan University, Wuxi, China.
Biophys J. 2021 Aug 17;120(16):3429-3436. doi: 10.1016/j.bpj.2021.05.028. Epub 2021 Jun 25.
Complex salt bridges, on which three or more charged residues interplay simultaneously, cannot be considered as addition of individual salt bridges. This is still an intriguing problem in protein folding and stability. Here, we used an obligated ABC-type collagen heterotrimer as a platform to study the relationship between energetic contributions and conformational details of three-body complex salt bridges anchored by positively charged residues, K and R. Eight complex salt bridges were constructed by engineering point mutations in the heterotrimer. The circular dichroism measurements showed that the K-anchored complex salt bridges were stronger than the R-anchored ones. The molecular dynamics simulation revealed that both types of salt bridges had distinct dynamic features. The energetic contribution of K-anchored salt bridges was mainly determined by strong single bridges. In the R-anchored complex salt bridges, both side-chain electrostatic interactions and side-chain-backbone hydrogen bonding were involved. An empirical equation was proposed to predict the energetic contributions with high accuracy (R = 0.93). This work could help us take insights into the mechanisms of composition-dependent behaviors of the complex salt bridges on protein surface.
复杂盐桥由三个或更多带电荷的残基同时相互作用，不能被视为单个盐桥的加和。这在蛋白质折叠和稳定性方面仍然是一个有趣的问题。在这里，我们使用一种必需的 ABC 型胶原三聚体作为平台，研究由带正电荷的残基 K 和 R 锚定的三体复杂盐桥的能量贡献与构象细节之间的关系。通过在三聚体中进行定点突变，构建了 8 种复杂盐桥。圆二色性测量表明，K 锚定的复杂盐桥比 R 锚定的复杂盐桥更强。分子动力学模拟揭示了这两种类型的盐桥具有不同的动态特征。K 锚定盐桥的能量贡献主要由强单桥决定。在 R 锚定的复杂盐桥中，侧链静电相互作用和侧链-骨架氢键都参与其中。提出了一个经验公式，可以高精度地预测能量贡献（R=0.93）。这项工作可以帮助我们深入了解蛋白质表面上复杂盐桥组成依赖性行为的机制。
