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The active site of magnesium chelatase

DOI: 10.1038/s41477-020-00806-9 DOI Help

Authors: Nathan B. P. Adams (The University of Sheffield) , Claudine Bisson (The University of Sheffield) , Amanda A. Brindley (The University of Sheffield) , David A. Farmer (The University of Sheffield) , Paul A. Davison (The University of Sheffield) , James D. Reid (The University of Sheffield) , C. Neil Hunter (The University of Sheffield)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Plants , VOL 104

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 8987 , 12788

Abstract: The insertion of magnesium into protoporphyrin initiates the biosynthesis of chlorophyll, the pigment that underpins photosynthesis. This reaction, catalysed by the magnesium chelatase complex, couples ATP hydrolysis by a ChlID motor complex to chelation within the ChlH subunit. We probed the structure and catalytic function of ChlH using a combination of X-ray crystallography, computational modelling, mutagenesis and enzymology. Two linked domains of ChlH in an initially open conformation of ChlH bind protoporphyrin IX, and the rearrangement of several loops envelops this substrate, forming an active site cavity. This induced fit brings an essential glutamate (E660), proposed to be the key catalytic residue for magnesium insertion, into proximity with the porphyrin. A buried solvent channel adjacent to E660 connects the exterior bulk solvent to the active site, forming a possible conduit for the delivery of magnesium or abstraction of protons.

Journal Keywords: Photosynthesis; Structure determination

Subject Areas: Biology and Bio-materials


Instruments: I02-Macromolecular Crystallography , I03-Macromolecular Crystallography , I04-Macromolecular Crystallography , I24-Microfocus Macromolecular Crystallography

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