Zhuang P, Blackburn M N, Peterson C B
Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, USA.
J Biol Chem. 1996 Jun 14;271(24):14323-32. doi: 10.1074/jbc.271.24.14323.
Upon treatment with denaturing agents, vitronectin has been observed to exhibit conformational alterations which are similar to the structural changes detected when vitronectin binds the thrombin-antithrombin complex or associates with the terminal attack complex of complement. Denaturation and renaturation of vitronectin isolated from human plasma were characterized by changes in intrinsic fluorescence. Unfolding by chemical denaturants was irreversible and accompanied by self-association of the protein to form vitronectin multimers. Self-association was evaluated by equilibrium analytical ultracentrifugation which demonstrated that multimers form only during the refolding process after removal of denaturant, that multimeric vitronectin dissociates to constituent subunits readily upon treatment with chemical denaturant, and that intermolecular disulfide cross-linking occurs primarily at the dimer level among a subset of constituent vitronectin subunits within the multimer. The monomeric form of vitronectin isolated from human plasma partially unfolds at intermediate concentrations of denaturant to an altered conformation with a high propensity to associate into multimers. Folding of vitronectin in vivo appears to be regulated by partitioning of folding intermediates toward either of two conformations, one that exists as a stable monomer and another that associates into a multimeric form.
在用变性剂处理后，已观察到玻连蛋白会出现构象改变，这些改变类似于玻连蛋白结合凝血酶 - 抗凝血酶复合物或与补体末端攻击复合物结合时检测到的结构变化。从人血浆中分离出的玻连蛋白的变性和复性通过内在荧光的变化来表征。化学变性剂引起的展开是不可逆的，并且伴随着蛋白质的自我缔合形成玻连蛋白多聚体。通过平衡分析超速离心评估自我缔合，结果表明多聚体仅在去除变性剂后的重折叠过程中形成，多聚体玻连蛋白在用化学变性剂处理后很容易解离成组成亚基，并且分子间二硫键交联主要发生在多聚体内一部分组成玻连蛋白亚基之间的二聚体水平。从人血浆中分离出的玻连蛋白单体形式在中等浓度的变性剂下会部分展开为一种改变的构象，这种构象很容易缔合成多聚体。玻连蛋白在体内的折叠似乎是通过折叠中间体向两种构象之一的分配来调节的，一种构象以稳定的单体形式存在，另一种构象则缔合成多聚体形式。
