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研究ANX A5的N-末端存在与否对其核心区域结构以及四级结构的影响.ANX家族蛋白的显著特征是含有高度保守的C-端核心序列以及多变的N-末端结构,核心序列由4个重复的同源序列构成,具有明显的同源性,而N-末端的序列及长度在进化过程中表现出很大的多样性.为了研究N-末端对ANX蛋白的意义,文章以ANX A5为例,采用分子动力学模拟的手段分别对ANX A5单体和三聚体进行了模拟,研究N-末端对ANX A5的核心区域结构以及四级结构的影响.模拟结果显示,N-末端存在与否并不影响ANX A5单体/亚基的结构,对钙离子的结合也没有大的影响;但是N-末端存在与否对ANX A5核心序列四级结构造成了很大的影响,三聚体有加速分散的趋势,从而猜测N-末端对ANX A5的亚基之间聚合有重要作用.综上可得,N-末端存在与否不会对其核心区域的结构稳定以及与Ca2+的结合造成大的影响,但是对于ANX A5三聚体结构的形成是必不可少的.","To study the influence of N-terminus of ANX A5 on its monomer and trimer structure,the annexin core,composed of four (eight in annexin A6) homologous domains of about 70 amino acids,shares an overall shape of a slightly bent dish.Calcium-and phospholipid-binding sites are located on the convex side while the N-terminus links domains Ⅰ and Ⅳ on the concave side.In contrast to the homologous annexin core,sequence analysis shows great diversity acquired by their N-terminus during evolution.Even though the N-terminus of annexins is much smaller than the C-terminuscore,it is essentially involved in the structural and functional peculiarities of each member of theprotein family.ANX A5 was the first member of annexins family to be crystallized andstudied by X-ray diffraction.In recent years,there have been a lot of research work about ANX A5 core,while the study of the structure and function of N-terminus is still scarce.Molecular dynamics simulations provide a tool through that we can study the influence of N-terminus at the atomic level.Based on the crystal structure of protein,we investigate whether the N-terminus of ANX A5 affects its monomer and trimer structure by molecular dynamics simulations.The presence or absence of the N-terminus doesn't influence the overall structure of ANX A5 monomer/subunit and has no effect on the binding of calcium ions.However,removal of the N-terminus leads to accelerated dissociation tendency of ANX A5 trimer,indicating that N-terminus affects the quateary structure of the protein.The truncated of N-terminus,we speculate,will block the formation of trimer and affect the normal physiological function of ANX A5.In conclusion,the presence or absence of the N-terminus doesn't influence the overall structure of ANX A5 monomer/subunit,while the N-terminus of ANX A5 is indispensable to the formation of trimer.