大米蛋白二级结构共架改性及增溶机理研究

Rice proteins (RPs) are typical grain proteins of high nutritional value. However, the hydrophobic tertiary structures strictly restrict the solubility, processibility, and therefore industrialization of RPs. Developing a green, efficient technique improving the solubility, processibility, and industrialization of RPs is challenging and imperative. Based on heterologous protein (protein-protein’) co-construction technique, this proposal aims to investigate the co-assembly of secondary structures of different protein origins to reconstruct the tertiary structures and improve the solubility of RPs. In detail, the first objective is to study the interactions of protein-protein’ secondary structures of based on their molten globular state. The second objective is to unveil the mechanism of reconstruction of tertiary structures of RPs following structural interactions. By clarifying the relationship between structural alterations and hydration effects of proteins, the last objective is to highlight the principle of the formation of soluble protein composites, and, as a result, to design protein complexes with controllable functionalities. Based on these studies, the following key questions are to be answered: how does the co-assembly of secondary structures affect the evolution and stability of reconstructed tertiary structures; the mechanistic effects of the chain stiffness and mobility on the hydration layer of protein composites? The project is to establish the theoretical basis for reconstructing of tertiary structures of RPs, and to enrich the techniques of modifications of hydrophobic proteins exemplified by RPs.

大米蛋白是优质谷物蛋白的典型，但其疏水性的三级结构导致溶解性差、加工性低，制约了其产业化发展。亟需开发绿色高效的增溶技术，提升大米蛋白的加工性及产业应用水平。本项目提出采用蛋白质-蛋白质’结构共架技术，通过改变大米蛋白二级结构的架构方式重建其三级结构，实现大米蛋白的高效增溶，拟从三个方面展开研究：1、构建蛋白质溶融态反应体系，探索蛋白质-蛋白质’共架结构的成型过程；2、通过酸中和解除溶融态环境，研究二级结构共架行为重建蛋白质三级结构的分子机制；3、考察共架蛋白的结构特性及溶剂化水平，揭示共架体形成的分子机理，并实现其功能性的可控设计。从而解决两个关键科学问题：二级结构共架行为对三级结构演变及稳定性的作用机理是什么；共架链的结构强度及流动性如何影响其水化层强度及水合效应？最终建立大米蛋白三级结构重建的理论模型，丰富以大米蛋白为代表的疏水性蛋白质高级结构的改性手段。

背景：大米蛋白是一种极具营养价值的植物蛋白，同时具有较低的免疫原性，可作为婴幼儿食品的蛋白质来源。但是，特殊的氨基酸序列形成反平行β-折叠为代表的保守二级结构，其形成的具有强表面疏水性的高级结构极大地限制了大米蛋白的溶解性和加工性，影响了大米蛋白的产业化应用。因此，在维持一级结构不变的基础上，从分子水平上改变大米蛋白二级结构的架构方式，以实现其三级结构的重建、提高其水溶性是十分必要的。. 主要研究内容：针对大米蛋白的难溶性问题，围绕二级结构，建立其与特定外源蛋白（酪蛋白或豌豆蛋白）结构共架（co-construction）的研究方法；阐明异源蛋白（蛋白质-蛋白质’）二级结构共架行为的产生及三级结构重建的分子机理；最后，从界面学角度揭示大米蛋白结构变化与水合效应及功能性之间的构效关系。. 重要结果：（1）在酪蛋白存在条件下，大米蛋白经pH循环处理后溶解度从<1.7%提升至90%以上；（2）阐明了异源蛋白二级结构共架行为的产生及三级结构重建的分子机理；（3）揭示了大米蛋白结构变化与水合效应及功能性之间的构效关系。. 科学意义：通过项目的实施，建立了大米蛋白三级结构重建的理论模型，丰富了以大米蛋白为代表的疏水性蛋白质高级结构的改性手段。