基于胶原异三聚体的成骨不全症机理研究

Mechanism of osteogenesis imperfecta based on collagen heterotrimer

胶原蛋白是细胞外基质的主要成分,由3条链缠绕构成三螺旋.在28种天然胶原中占比最大的是Ⅰ型胶原蛋白,它是由两条a1链与一条a2链构成的异三聚体,a1或a2链中甘氨酸单点突变会导致成骨不全症.基于更接近天然胶原的异三聚体模型(abc),3条链中分别引入Gly→Ala,构建7种突变体.差示扫描量热结果表明,单点突变体的熔融温度(Tm)值降低15℃,双点及三点突变体未形成三螺旋结构.利用梯阶模型分析分子动力学模拟轨迹,突变点附近梯阶参数值发生变化,表明三螺旋结构局部解折叠.引入弹性函数量化胶原结构变化程度,发现氢键能量与结构形变分数具有高关联性(R2=0.76),表明突变不仅破坏了氢键作用力,也导致了分子的弯曲与运动状态的变化.结合计算与实验,解析了甘氨酸突变对胶原整体结构与运动模式的影响,为进一步揭示甘氨酸突变的致病机理提供了理论基础.

In this study,Gly→Ala was introduced into three chains of the heterotrimeric model(abc);seven mutants were subsequently constructed,and the local structure and global motion changes were analyzed.DSC results showed that the Tm value of the single point mutation was reduced by about 15°C,while the double and triple point mutations did not form triple helical structures.MD simulation trajectories were analyzed by ladder models;the results showed that the value of the step parameter changes near the mutation point,indicating an unfolding of the triple helix structure.An elastic function was introduced to quantify the degree of collagen structure change.It was found that the hydrogen bond energy was highly R2=0.76correlated with the structural deformation fraction(),indicating that the mutation not only destroyed the hydrogen bond force,but also resulted in changes in the bending and motion states of the molecule.This study,combined with calculations and experiments,helped quantify the effects of glycine mutation on the overall structure and movement pattern of collagen.Hence,the study provides a theoretical basis for clarifying the pathogenic mechanism of glycine mutation.