The unusual mycobacterial chaperonins: evidence for in vivo oligomerization and specialization of function
The unusual mycobacterial chaperonins: evidence for in vivo oligomerization and specialization of function
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DOI：
10.1111/j.1365-2958.2012.08150.x
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发表时间：
2012-09-01
影响因子：
3.6
通讯作者：
Lund, Peter A.
中科院分区：
文献类型：
--
作者：
Fan, MingQi;Rao, Tara;Lund, Peter A.
病原体结核分枝杆菌表达两种伴侣蛋白，一种（Cpn60.1）必需伴侣蛋白和一种（Cpn60.2）必需伴侣蛋白。据报道，这些蛋白质不形成寡聚体，尽管事实上伴侣蛋白的寡聚化被认为是其功能所必需的。我们在这里表明，从耻垢分枝杆菌Cpn60.2同源物也未能在标准条件下寡聚化。然而，我们也表明，Cpn60.2蛋白从两种生物体可以取代大肠杆菌的基本groEL基因，他们可以与大肠杆菌功能。coli GroES辅伴侣蛋白，以及与它们的同源辅伴侣蛋白，强烈暗示它们在体内形成寡聚体。我们发现Cpn60.1蛋白，而不是Cpn60.2蛋白，可以弥补M的损失。耻垢病cpn60.1基因。我们研究了寡聚化的Cpn60.2蛋白，使用分析超离心和质谱。两者都在标准条件下形成单体，但它们在亲液剂和ADP或ATP存在下形成更高级的低聚物。在这些条件下，它们的ATP酶活性显著增强。我们的结论是，基本的分枝杆菌伴侣蛋白，而不稳定的许多其他细菌伴侣蛋白相比，在体内作为低聚物，并有专门的功能的分枝杆菌伴侣蛋白基因复制。
The pathogen Mycobacterium tuberculosis expresses two chaperonins, one (Cpn60.1) dispensable and one (Cpn60.2) essential. These proteins have been reported not to form oligomers despite the fact that oligomerization of chaperonins is regarded as essential for their function. We show here that the Cpn60.2 homologue from Mycobacterium smegmatis also fails to oligomerize under standard conditions. However, we also show that the Cpn60.2 proteins from both organisms can replace the essential groEL gene of Escherichia coli, and that they can function with E. coli GroES cochaperonin, as well as with their cognate cochaperonin proteins, strongly implying that they form oligomers in vivo. We show that the Cpn60.1 proteins, but not the Cpn60.2 proteins, can complement for loss of the M. smegmatis cpn60.1 gene. We investigated the oligomerization of the Cpn60.2 proteins using analytical ultracentrifugation and mass spectroscopy. Both form monomers under standard conditions, but they form higher order oligomers in the presence of kosmotropes and ADP or ATP. Under these conditions, their ATPase activity is significantly enhanced. We conclude that the essential mycobacterial chaperonins, while unstable compared to many other bacterial chaperonins, do act as oligomers in vivo, and that there has been specialization of function of the mycobacterial chaperonins following gene duplication.