Crystal structure of the catalytic subunit of magnesium chelatase

分类： 生物学 >> 生物物理学 提交时间： 2016-05-12

Chen, Xuemin Pu, Hua Fang, Ying Wang, Xiao Zhao, Shun Dai, Huai-En Liu, Lin Chen, Xuemin Pu, Hua Fang, Ying Wang, Xiao Zhao, Shun Lin, Yajing Gong, Weimin Zhang, Min Gong, Weimin

摘要： Tetrapyrroles, including haem and chlorophyll, play vital roles for various biological processes, such as respiration and photosynthesis, and their biosynthesis is critical for virtually all organisms. In photosynthetic organisms, magnesium chelatase (MgCh) catalyses insertion of magnesium into the centre of protoporphyrin IX, the branch-point precursor for both haem and chlorophyll, leading tetrapyrrole biosynthesis into the magnesium branch1,2. This reaction needs a cooperated action of the three subunits of MgCh: the catalytic subunit ChlH and two AAA(+) subunits, ChlI and ChlD ( refs 3-5). To date, the mechanism of MgCh awaits further elucidation due to a lack of high-resolution structures, especially for the similar to 150 kDa catalytic subunit. Here we report the crystal structure of ChlH from the photosynthetic cyanobacterium Synechocystis PCC 6803, solved at 2.5 angstrom resolution. The active site is buried deeply inside the protein interior, and the surrounding residues are conserved throughout evolution. This structure helps to explain the loss of function reported for the cch and gun5 mutations of the ChlH subunit, and to provide the molecular basis of substrate channelling during the magnesium-chelating process. The structure advances our understanding of the holoenzyme of MgCh, a metal chelating enzyme other than ferrochelatase.

同行评议状态:待评议

 点击量 2763  下载量 1422  评论