链霉亲和素的结构研究绑定循环。
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Freitag年代,Le阮富仲我Klumb L, Stayton PS, Stenkamp再保险
链霉亲和素的结构研究绑定循环。
蛋白质科学。1997年6月,6 (6):1157 - 66。
- PubMed ID
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9194176 (在PubMed]
- 文摘
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streptavidin-biotin复杂提供了许多重要的生物技术应用的基础,是一个有趣的模型系统研究的高亲和性protein-ligand交互。这里报告晶体构象的研究阐明灵活绑定循环链霉亲和素(残留45 - 52)释放和约束形式。的晶体结构的链霉亲和素已经确定在两个单斜晶体形式。绑定循环通常采用的开放构型的物种。在一个单元的晶体形式,灵活的循环采用封闭的构象和填料的相互作用的分析表明,蛋白质接触稳定闭环构象。在其他晶体形成循环采用开放的构象。Co-crystallization链霉亲和素与生物素导致两个额外的,不同的晶体形式,与配体结合的四个结合位点的第一晶体形成和生物素只有两个单元。生物素的主要变化与绑定是表面的闭合循环将残留45 - 52。残留49至52显示3(10)螺旋构象的子单元的结构而不是无序循环中观察到其他链霉亲和素的结构决定。此外,开放构型由β褶板之间的氢键稳定残留45和52,不能发生在封闭的构象。 The 3(10) helix is observed in nearly all unbound subunits of both the co-crystallized and ligand-free structures. An analysis of the temperature factors of the binding loop regions suggests that the mobility of the closed loops in the complexed structures is lower than in the open loops of the ligand-free structures. The two biotin bound subunits in the tetramer found in the MONO-b1 crystal form are those that contribute Trp 120 across their respective binding pockets, suggesting a structural link between these binding sites in the tetramer. However, there are no obvious signatures of binding site communication observed upon ligand binding, such as quaternary structure changes or shifts in the region of Trp 120. These studies demonstrate that while crystallographic packing interactions can stabilize both the open and closed forms of the flexible loop, in their absence the loop is open in the unbound state and closed in the presence of biotin. If present in solution, the helical structure in the open loop conformation could moderate the entropic penalty associated with biotin binding by contributing an order-to-disorder component to the loop closure.