Schulze A J, Quarzago D, Andreasen P A
Max-Planck-Institut für Biochemie, Abteilung Strukturforschung, Planegg-Martinsried, Germany.
Eur J Biochem. 1996 Sep 15;240(3):550-5. doi: 10.1111/j.1432-1033.1996.0550h.x.
Type-1 plasminogen-activator inhibitor (PAI-1) was studied by Fourier-transform infrared spectroscopy, far-ultraviolet CD spectroscopy, and fluorescence-emission spectroscopy, with the aim to obtain structural information about its active form. The spectra of latent, active and reactive-center-cleaved forms of PAI-1 produced by HT-1080 cells were different. While the cleaved and the latent forms were similar with regard to their beta-structure content, comparison of the spectra of these forms with the spectra of active PAI-1 suggested a much higher degree of unordered structure for the active form compared with the latent and reactive-center-cleaved forms than previously assumed. We discuss our results with reference to the known three-dimensional X-ray structures of latent PAI-1, of reactive-center-cleaved serpins, including reactive-center-cleaved PAI-1, and of intact serpins, and with reference to previous results on the differences in the affinity of mAbs for the different PAI-1 forms. We interpret our results in favor of a global rearrangement of secondary structure during latency transition and reactive-center cleavage in PAI-1, not only involving the reactive-center loop and parts of beta-sheets A and C, but also the "rear' side of the molecule, such as helices H and G. Thus, we suggest flexibility in serpin structural elements that were previously regarded as rigid.
采用傅里叶变换红外光谱、远紫外圆二色光谱和荧光发射光谱对1型纤溶酶原激活物抑制剂（PAI-1）进行了研究，旨在获取其活性形式的结构信息。HT-1080细胞产生的PAI-1的潜伏型、活性型和反应中心裂解型的光谱各不相同。虽然裂解型和潜伏型在β结构含量方面相似，但将这些形式的光谱与活性PAI-1的光谱进行比较表明，与潜伏型和反应中心裂解型相比，活性形式的无序结构程度比以前设想的要高得多。我们结合潜伏型PAI-1、反应中心裂解的丝氨酸蛋白酶抑制剂（包括反应中心裂解的PAI-1）和完整丝氨酸蛋白酶抑制剂的已知三维X射线结构，以及先前关于单克隆抗体对不同PAI-1形式亲和力差异的结果，对我们的结果进行了讨论。我们认为我们的结果支持PAI-1在潜伏转变和反应中心裂解过程中二级结构的整体重排，这不仅涉及反应中心环以及β折叠A和C的部分，还涉及分子的“背面”，如螺旋H和G。因此，我们认为先前被认为是刚性的丝氨酸蛋白酶抑制剂结构元件具有灵活性。
