Guillet V, Lapthorn A, Hartley R W, Mauguen Y
Laboratoire de Physique, CNRS, UPR 180, Centre d'Etudes Pharmaceutiques, 92296 Châtenay-Malabry Cedex, France.
Structure. 1993 Nov 15;1(3):165-76. doi: 10.1016/0969-2126(93)90018-c.
Protein-protein recognition is fundamental to most biological processes. The information we have so far on the interfaces between proteins comes largely from several protease-inhibitor and antigen-antibody complexes. Barnase, a bacterial ribonuclease, and barstar, its natural inhibitor, form a tight complex which provides a good model for the study and design of protein-protein non-covalent interactions.
Here we report the structure of a complex between barnase and a fully functional mutant of barstar determined by X-ray analysis. Barstar is composed of three parallel alpha-helices stacked against a three-stranded parallel, beta-sheet, and sterically blocks the active site of the enzyme with an alpha-helix and adjacent loop. The buried surface in the interface between the two molecules totals 1630 A2. The barnase-barstar complex is predominantly stabilized by charge interactions involving positive charges in the active site of the enzyme. Asp39 of barstar binds to the phosphate-binding site of barnase, mimicking enzyme-substrate interactions.
The phosphate-binding site of the enzyme is the anchor point for inhibitor binding. We propose that this is also likely to be the case for other ribonuclease inhibitors.
蛋白质-蛋白质识别是大多数生物过程的基础。我们目前所掌握的关于蛋白质间界面的信息，很大程度上来自于几种蛋白酶-抑制剂和抗原-抗体复合物。芽孢杆菌RNA酶（Barnase）是一种细菌核糖核酸酶，其天然抑制剂芽孢杆菌抗酶（Barstar）形成紧密复合物，为蛋白质-蛋白质非共价相互作用的研究和设计提供了良好模型。
本文报道了通过X射线分析确定的Barnase与Barstar一个功能完全的突变体之间复合物的结构。Barstar由三条平行的α螺旋堆叠在一个三链平行的β折叠片上组成，并用一个α螺旋和相邻的环在空间上阻断酶的活性位点。两个分子界面处的埋藏表面积总计1630 Ų。Barnase-Barstar复合物主要通过涉及酶活性位点正电荷的电荷相互作用而稳定。Barstar的Asp39与Barnase的磷酸结合位点结合，模拟酶-底物相互作用。
酶的磷酸结合位点是抑制剂结合的锚定点。我们认为其他核糖核酸酶抑制剂可能也是如此。
