Murry-Brelier A, Goldberg M E
Département de Biochimie et Génétique Moléculaire, Institut Pasteur, Paris, France.
Biochemistry. 1988 Oct 4;27(20):7633-40. doi: 10.1021/bi00420a010.
A reversible acid-denaturation process of the beta 2 subunit of Escherichia coli tryptophan synthase has been set up. The acid-denatured state has been physically characterized: though not in a random-coiled conformation, it is extensively denatured. The renaturation of this denatured state of beta 2 has been observed in a stopped-flow system, in the presence of a monoclonal antibody directed against native beta 2. It is shown that the association occurs very early in the folding of beta 2. The association rate constants of the antibody with the immunoreactive folding intermediate and with native beta 2 are the same (3 X 10(5) M-1.s-1). But at high antibody concentrations the formation of the antigen/antibody complex is rate limited by a rapid (5.4 X 10(-2) s-1) isomerization of refolding beta chains. This isomerization appears to reflect the formation of at least part of the epitope recognized by the antibody during the folding of beta 2. Further conformational adjustments occurring later in the folding pathway would then allow the ultimate structuring of the epitope.
已建立大肠杆菌色氨酸合酶β2亚基的可逆酸变性过程。对酸变性状态进行了物理表征：尽管不是随机卷曲构象，但它已广泛变性。在停流系统中，在存在针对天然β2的单克隆抗体的情况下，观察到β2这种变性状态的复性。结果表明，结合发生在β2折叠的早期。抗体与免疫反应性折叠中间体以及与天然β2的结合速率常数相同（3×10⁵ M⁻¹·s⁻¹）。但在高抗体浓度下，抗原/抗体复合物的形成受重折叠β链快速（5.4×10⁻² s⁻¹）异构化的速率限制。这种异构化似乎反映了在β2折叠过程中抗体识别的至少部分表位的形成。折叠途径后期发生的进一步构象调整将使表位最终形成结构。
