Staley J P, Kim P S
Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Department of Chemistry, Nine Cambridge Center, MA 02142.
Proc Natl Acad Sci U S A. 1992 Mar 1;89(5):1519-23. doi: 10.1073/pnas.89.5.1519.
In the oxidative folding of bovine pancreatic trypsin inhibitor (BPTI) at neutral pH, only two one-disulfide intermediates accumulate to a significant extent, namely [5-55] and [30-51]. In this paper we describe a recombinant model of [5-55], designated [5-55]Ala, which was made by replacing the cysteine residues not involved in the disulfide bond with alanine. As judged by two-dimensional NMR, [5-55]Ala folds into essentially the same conformation as native BPTI. Moreover, like native BPTI, [5-55]Ala inhibits trypsin stoichiometrically. Thus, the disulfide-bonded intermediate [5-55] corresponds not to a partially folded protein folding intermediate but rather to an essentially completely folded protein. This conclusion provides an explanation for many of the thermodynamic and kinetic properties of [5-55] in the folding pathway of BPTI.
在中性pH条件下牛胰蛋白酶抑制剂（BPTI）的氧化折叠过程中，只有两种单二硫键中间体能够大量积累，即[5-55]和[30-51]。在本文中，我们描述了一种[5-55]的重组模型，命名为[5-55]Ala，它是通过将不参与二硫键形成的半胱氨酸残基替换为丙氨酸而构建的。通过二维核磁共振判断，[5-55]Ala折叠成与天然BPTI基本相同的构象。此外，与天然BPTI一样，[5-55]Ala能化学计量地抑制胰蛋白酶。因此，二硫键连接的中间体[5-55]并非对应于部分折叠的蛋白质折叠中间体，而是对应于一种基本完全折叠的蛋白质。这一结论为BPTI折叠途径中[5-55]的许多热力学和动力学性质提供了解释。
