中文摘要：

大肠杆菌热休克蛋白DegP，也称作HtrA或蛋白酶Do，具有分子伴侣和蛋白酶两种活性。缺失DegP会导致大肠杆菌在高温下不能存活。DegP的晶体结构表明，它是由两个紧密折叠的三聚体松散地结合在一起形成的六聚体。作者在分子筛柱层析的实验中发现DegP六聚体与变性的α-lactalbumin共孵育后能全部转变为更大的寡聚体。进一步用负染电镜及单颗粒三维重构方法对该寡聚体进行结构分析，发现它是由4个三聚体组成的具有四面体对称性的十二聚体笼形结构。文章还对DegP十二聚体的结构与功能的关系展开了初步的讨论。

英文摘要：

Escherichia coli heat shock protein DegP, also known as HtrA and protease Do, was found to exhibit dual activities as a protease and a molecular chaperone. The activities of DegP are indispensable for cells to grow at elevated temperatures. Its crystal structure was revealed to be a hexamer formed through staggered association of two trimeric rings. In the present work, we demonstrated that the DegP hexamers convert to larger oligomers upon binding to the unfolded α-lactulbumin by gel titration experiments. The negatively stained specimens of these oligomers were subjected to electron microscopy analysis and single particle reconstruction. The results revealed that they are cage-like dedecamers composed of 4 trimers in a tetrahedral symmetry. Referred to previous publications, we then suggest that they may represent the status of DegP in protease and chaperone activities and are thus functionally important.