当前位置: X-MOL 学术Biochimie › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Structure basis of the improved sweetness and thermostability of a unique double-sites single-chain sweet-tasting protein monellin (MNEI) mutant
Biochimie ( IF 3.9 ) Pub Date : 2018-09-06 , DOI: 10.1016/j.biochi.2018.08.010
Meng Zhao , Xiangqun Xu , Bo Liu

The sweet protein monellin has an intensely sweet potency but limited stability. We have identified a double-sites mutant (E2N/E23A) of the single-chain monellin (MNEI) with both improved sweetness (about 3-fold) and thermostability (10 °C). However, the structural basis of its superior properties remains elusive until now. Herein we report its crystal structure at a resolution 1.90 Å. Similar to the wild-type, E2N/E23A adopts a wedge-shaped structure consisting of a five-strand β-sheet partially “wrapped” around an α-helix. However, distinguishing parts were present in the loops region, including a remarkable conformation shift from β-strand to loop around residue R39. Molecular docking revealed the persistence of conserved protein-receptor interface and formation of new intermolecular ionic bonds in the E2N/E23A-receptor complex involving the taste-active residue R39 of the sweet protein, which could account for its significant improvement of sweetness. On the other hand, a rearrangement of intramolecular interaction network including the C-H … π bond between A23 and F89 that led to enhanced hydrophobicity in the protein core, could be correlated with its improved thermostability. Furthermore, two new sweeter mutants of MNEI were created. These findings highlight the critical roles of key sweetness determinant residue R39 and hydrophobicity at the protein core for the sweetness and thermostability of the protein, respectively, which thus provide a deeper insight for understanding the structure-function relationship of the sweet protein as well as guidance for rational design of this unique biomacromolecule.



中文翻译:

独特的双位点单链甜味蛋白莫内林(MNEI)突变体提高的甜度和热稳定性的结构基础

甜蛋白monellin具有强烈的甜味力,但稳定性有限。我们已经确定了单链monellin(MNEI)的双位点突变体(E2N / E23A),具有改善的甜度(约3倍)和热稳定性(10°C)。但是,迄今为止,其优越性能的结构基础仍然难以捉摸。在此,我们报告其晶体结构的分辨率为1.90Å。与野生型相似,E2N / E23A采用楔形结构,该结构由部分“包裹”在α螺旋周围的五链β折叠组成。然而,在环区域中存在区别部分,包括与β明显的构象偏移-链环绕残基R39。分子对接揭示了保守的蛋白质-受体界面的持久性以及在E2N / E23A-受体复合物中涉及甜蛋白的味觉活性残基R39的新分子间离子键的形成,这可以解释其甜度的显着提高。另一方面,分子内相互作用网络的重排(包括A23和F89之间的CH…π键)导致蛋白质核心的疏水性增强,可能与其热稳定性提高有关。此外,创建了两个新的更甜的MNEI突变体。这些发现凸显了关键的甜度决定因素残基R39和蛋白质核心的疏水性分别对蛋白质的甜度和热稳定性的关键作用,

更新日期:2018-09-06
down
wechat
bug