Wang J, Reich E
Department of Pharmacological Sciences, State University of New York, Stony Brook 11794, USA.
Protein Sci. 1995 Sep;4(9):1768-79. doi: 10.1002/pro.5560040912.
We have used a group of human microplasminogens (mPlg), modified by residue substitutions, insertions, deletions, and chain breaks (1) to study the determinants of productive interactions with two plasminogen activators, urokinase (uPA), and streptokinase (SK); (2) to explore the basis of species specificity in the zymogen-SK complex activity; and (3) to compare active SK complex formation in mPlg and microplasmin (mPlm). Modifications within the disulfide-bonded loop containing the activation site and the adjacent hexadecapeptide upstream sequence showed that uPA recognition elements encompassed R29 at the activation site and multiple elements extending upstream to perhaps 13 residues, all maintained in specific conformational register by surrounding pairs of disulfide bonds. A generally parallel pattern of structural requirements was observed for active zymogen-SK complex formation. Changes within the loop downstream of the activation site were tolerated well by uPA and poorly by SK. The introduction of selected short bovine (Plg) sequences in human mPlg reduced the activity of the resulting SK complexes. The requirements for active SK complex formation are different for mPlg and mPlm.
我们使用了一组经残基替换、插入、缺失和链断裂修饰的人微纤溶酶原（mPlg）：（1）研究与两种纤溶酶原激活剂，即尿激酶（uPA）和链激酶（SK）发生有效相互作用的决定因素；（2）探索酶原-SK复合物活性中物种特异性的基础；（3）比较mPlg和微纤溶酶（mPlm）中活性SK复合物的形成情况。对包含激活位点的二硫键连接环及其上游相邻的十六肽序列进行修饰后发现，uPA识别元件包括激活位点处的R29以及向上游延伸至约13个残基的多个元件，所有这些元件通过周围的二硫键对保持在特定的构象排列中。对于活性酶原-SK复合物的形成，观察到了大致平行的结构要求模式。激活位点下游环内的变化，uPA耐受性良好，而SK耐受性较差。在人mPlg中引入选定的短牛（Plg）序列会降低所得SK复合物的活性。mPlg和mPlm形成活性SK复合物的要求不同。
