硼酸盐对抗冻糖蛋白结构的影响

抗冻糖蛋白通过吸附-抑制机理阻止细胞内部冰晶积累，有利于极地地区各物种的生存. 硼酸盐缓冲剂抑制抗冻糖蛋白抗冻活性已被广泛认为是支持羟基作为冰结合位点而非甲基结合的直接实验证据. 另一方面，硼酸盐结合可能对抗冻糖蛋白构象产生影响，但还没有被定量研究. 本文使用副本交换分子动力学模拟研究了溶液中单个硼酸根阴离子结合到AFGP8上引起的蛋白结构扰动. 在冰点附近，这种结合不仅使与硼酸盐结合的二糖相邻的二糖基团彼此靠近，而且影响AFGP8的整体构象. 硼酸盐与不同二糖侧链结合引起的结构变化表现出明确的位点特异性，并且硼酸盐结合对结构变化的影响在高温下显着降低.

Impact of Borate on Structure of Antifreeze Glycoproteins

Antifreeze glycoproteins(AFGPs) facilitate the survival of various organ-isms in the polar region by preventing internal ice accumulation via an adsorption-inhibition mechanism. Inhibition of AFGP antifreeze activity by the borate buffers has been widely acknowledged as the direct experimental evidence supporting the hydroxyl, rather than methyl, binding mechanism. On the other hand, perturbation of borate binding on the AFGP con guration, which might have considerable influence on the binding efficiency of not only the hydroxyl but also the methyl groups, has rarely been quantitatively examined. Herein we studied, using molecular dynamics simulations, the perturbation on the configuration of a solvated AFGP8 protein induced by the binding of one single borate anion. Near the freezing point, this binding not only makes the disaccharide groups adjacent to the borate-binding disaccharide close to each other but also affects the entire AFGP8 conformation. The structural changes induced by the binding of borate on different disaccharide sidechains exhibit clear site-specificities and the effect of borate binding on the structural changes is significantly reduced at higher temperatures. Our study is valuable for further understanding the relationship between the structure and antifreeze activity of these antifreeze glycoproteins.