Subjects: Biology >> Biophysics submitted time 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
Abstract： 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.
Peer Review Status:
Awaiting Review
Subjects: Biology >> Biophysics submitted time 2016-05-11
Abstract： Adaptations to hypoxia play an important role in Mycobacterium tuberculosis pathogenesis. Rv0324, which contains an HTH DNA-binding domain and a rhodanese domain, is one of the key transcription regulators in response to hypoxia. M. tuberculosis Rv1674c is a homologue of Rv0324. To understand the interdomain interaction and regulation of the HTH domain and the rhodanese domain, recombinant Rv1674c protein was purified and crystallized by the vapour-diffusion method. The crystals diffracted to 2.25 angstrom resolution. Preliminary diffraction analysis suggests that the crystals belonged to space group P3(1)21 or P3(2)21, with unit-cell parameters a = b = 67.8, c = 174.5 angstrom, alpha = beta = 90, gamma = 120 degrees. The Matthews coefficient was calculated to be 2.44 angstrom(3) Da(-1), assuming that the crystallographic asymmetric unit contains two protein molecules.
Peer Review Status:Awaiting Review
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