小角X-射线散射与结构预测法研究中国人乳β-酪蛋白的3级结构

Studying Tertiary Structure of Human β-Casein by Using Small-angle X-ray Scattering and Structure Prediction

通过小角X-射线散射与结构预测的方法研究人乳β-酪蛋白的3级结构,并分析其生理功能。通过使用DEAE Sepharose FAST Flow琼脂糖凝胶获得纯度大于90%的β-酪蛋白纯品,并对其溶液进行小角X-射线散射(0.2 mol磷酸盐缓冲溶液,10 mmol DTT,p H 6.7),将获得的人乳β-酪蛋白的结构信息与通过折叠识别及从头预测构建的预测模型进行比较,筛选出在试验条件下与试验结果最相符的人乳β-酪蛋白3级结构模型,该模型结构松散,含有较少的α-螺旋和β-折叠。同时结合模型对人乳β-酪蛋白磷酸化、糖基化及脂质化等蛋白质功能位点进行了分析,认为人乳β-酪蛋白含有12个可以与乳糖或葡萄糖结合的糖基化位点,7个脂质化位点,其磷酸化位点与已知的5个磷酸化位点相符。

This research studies on the tertiary structure of human β-Casein by using Small-angle X-ray Scattering and Structure Prediction, and then analysed its physiological functions. By using DEAE Sepharose FAST Flow agarose gel to get the Human β-Casein that their purity higher than 90%, and then analysed the solution（0.2 mol/L phosphate buffer, 10 mmol DTT, pH 6.7） through Small-angle X-ray Scattering. Comparing the structure information of Human β-Casein and the prediction models of fold recognition and ab initio, selected the model that was the most closed with the result of the experiment. This model is loosely in structure, containing less α helices and β fold. At the same time, we also had a brief analysis on the phosphorylation, glycosylation and Lipidated protein functional sites of Human β-Casein that comparing with the model. We thought there were 12 glycosylation sites that may combine with lactose and glucose and 7 lipidated sites in the Human β-Casein molecular. Its phosphorylation sites matched with five known phosphorylation sites.