Abolition of magnesium chelatase activity by the gun5 mutation and reversal by Gun4.
The chlorophyll-deficient gun5-1 and cch Arabidopsis mutants carry single point mutations in the CHLH subunit of the magnesium chelatase enzyme, which catalyses the first committed step of chlorophyll biosynthesis. Recombinant Synechocystis ChlH subunits carrying the gun5-1 or cch mutations are inactive in Mg-chelatase assays, despite being able to bind both substrate and product, and retaining a capacity to form a ChlH-ChlI-ChlD Mg-chelatase complex. These mutant subunits act as inhibitors of ChlH, showing that the ChlH-porphyrin complex associates reversibly with the ChlI and D subunits during the catalytic cycle. This inhibition is reversed upon addition of Gun4.
Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK.
Paul A
PA
Davison
C Neil
CN
Hunter
D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D055162:Biocatalysis; D015153:Blotting, Western; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D008190:Lyases / Q000235:genetics* / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation; D011166:Porphyrins / Q000378:metabolism; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; C472017:GUN4 protein, Arabidopsis; D047908:Intracellular Signaling Peptides and Proteins; D050505:Mutant Proteins; D011166:Porphyrins; D021122:Protein Subunits; D011994:Recombinant Proteins; D008190:Lyases; C086788:magnesium chelatase