【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。更多还原

【Abstract】 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-lactalbumin by gel fitration 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 dodecamers 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.更多还原