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六聚体 Rubisco 折叠和组装中的偶联伴侣作用。

Coupled chaperone action in folding and assembly of hexadecameric Rubisco.

机构信息

Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.

出版信息

Nature. 2010 Jan 14;463(7278):197-202. doi: 10.1038/nature08651.

Abstract

Form I Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase), a complex of eight large (RbcL) and eight small (RbcS) subunits, catalyses the fixation of atmospheric CO(2) in photosynthesis. The limited catalytic efficiency of Rubisco has sparked extensive efforts to re-engineer the enzyme with the goal of enhancing agricultural productivity. To facilitate such efforts we analysed the formation of cyanobacterial form I Rubisco by in vitro reconstitution and cryo-electron microscopy. We show that RbcL subunit folding by the GroEL/GroES chaperonin is tightly coupled with assembly mediated by the chaperone RbcX(2). RbcL monomers remain partially unstable and retain high affinity for GroEL until captured by RbcX(2). As revealed by the structure of a RbcL(8)-(RbcX(2))(8) assembly intermediate, RbcX(2) acts as a molecular staple in stabilizing the RbcL subunits as dimers and facilitates RbcL(8) core assembly. Finally, addition of RbcS results in RbcX(2) release and holoenzyme formation. Specific assembly chaperones may be required more generally in the formation of complex oligomeric structures when folding is closely coupled to assembly.

摘要

I 型 RuBisCO(核酮糖 1,5-二磷酸羧化酶/加氧酶)由 8 个大亚基(RbcL)和 8 个小亚基(RbcS)组成,催化光合作用中大气 CO2 的固定。RuBisCO 的有限催化效率激发了广泛的努力来重新设计该酶,以提高农业生产力。为了促进这些努力,我们通过体外重组和冷冻电子显微镜分析了蓝细菌 I 型 RuBisCO 的形成。我们表明,GroEL/GroES 分子伴侣介导的 RbcL 亚基折叠与由伴侣蛋白 RbcX(2)介导的组装紧密偶联。RbcL 单体仍然保持部分不稳定状态,并保持对 GroEL 的高亲和力,直到被 RbcX(2)捕获。如 RbcL(8)-(RbcX(2))(8)组装中间体的结构所示,RbcX(2)作为分子夹具稳定 RbcL 亚基作为二聚体,并促进 RbcL(8)核心组装。最后,添加 RbcS 导致 RbcX(2)释放和全酶形成。当折叠与组装紧密偶联时,特定的组装伴侣蛋白可能更普遍地需要用于复杂寡聚体结构的形成。

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