Magnesium-Protoporphyrin Chelatase of Rhodobacter sphaeroides: Reconstitution of Activity by Combining the Products of the bchH, -I, and -D Genes Expressed in Escherichia coli

Magnesium-protoporphyrin chelatase lies at the branch point of the heme and (bacterio) chlorophyll biosynthetic pathways. In this work, the photosynthetic bacterium Rhodobacter sphaeroides has been used as a model system for the study of this reaction. The bchH and the bchI and -D genes from R. spha...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1995-03, Vol.92 (6), p.1941-1944
Main Authors: Lucien C. D. Gibson, Willows, Robert D., Kannangara, C. Gamini, von Wettstein, Dieter, Hunter, C. Neil
Format: Article
Language:English
Subjects:
Absorption spectra
Adenosine Triphosphate - metabolism
Bacteria
Base Sequence
Biochemistry
Biosynthesis
Chelation
Chlorophyll
Cloning, Molecular
DNA Primers
Emission spectra
Enzymes
Escherichia coli
Flowers & plants
Fluorescence
Gene Expression
Genes
Genes, Bacterial
Kinetics
Lyases - biosynthesis
Lyases - genetics
Lyases - metabolism
Molecular Sequence Data
Multigene Family
Photosynthesis - genetics
Plants
Plasmids
Polymerase Chain Reaction
Protoporphyrins
Recombinant Proteins - biosynthesis
Recombinant Proteins - metabolism
Rhodobacter sphaeroides
Rhodobacter sphaeroides - enzymology
Rhodobacter sphaeroides - genetics
Spectrophotometry
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Summary:Magnesium-protoporphyrin chelatase lies at the branch point of the heme and (bacterio) chlorophyll biosynthetic pathways. In this work, the photosynthetic bacterium Rhodobacter sphaeroides has been used as a model system for the study of this reaction. The bchH and the bchI and -D genes from R. sphaeroides were expressed in Escherichia coli. When cell-free extracts from strains expressing BchH, BchI, and BchD were combined, the mixture was able to catalyze the insertion of Mg into protoporphyrin IX in an ATP-dependent manner. This was possible only when all three genes were expressed. The bchH, -I, and -D gene products are therefore assigned to the Mg chelatase step in bacteriochlorophyll biosynthesis. The mechanism of the Mg chelation reaction and the implications for chlorophyll biosynthesis in plants are discussed.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.92.6.1941