Broadened Substrate Specificity of 3-Hydroxyethyl Bacteriochlorophyllide a Dehydrogenase (BchC) Indicates a New Route for the Biosynthesis of Bacteriochlorophyll a
| Autor: | Christiane Lange, Jürgen Moser, Dieter Jahn, Svenja Kiesel, Simone Virus, Sabine Peters, Hugo Scheer |
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| Rok vydání: | 2015 |
| Předmět: |
Oxidoreductases Acting on CH-CH Group Donors
Molecular Sequence Data Gene Expression Dehydrogenase Crystallography X-Ray Biochemistry Cofactor Substrate Specificity Chlorobi chemistry.chemical_compound Protochlorophyllide Biosynthesis Bacterial Proteins Oxidoreductase Escherichia coli Amino Acid Sequence Photosynthesis Molecular Biology Magnesium ion chemistry.chemical_classification biology Chlorophyllides Sequence Homology Amino Acid Cell Biology Bacteriochlorophyll A NAD Recombinant Proteins chemistry biology.protein Mutagenesis Site-Directed Enzymology NAD+ kinase Bacteriochlorophyll Oxidoreductases Sequence Alignment |
| Zdroj: | The Journal of biological chemistry. 290(32) |
| ISSN: | 1083-351X |
| Popis: | Bacteriochlorophyll a biosynthesis requires formation of a 3-hydroxyethyl group on pyrrole ring A that gets subsequently converted into a 3-acetyl group by 3-vinyl bacteriochlorophyllide a hydratase (BchF) followed by 3-hydroxyethyl bacteriochlorophyllide a dehydrogenase (BchC). Heterologous overproduction of Chlorobaculum tepidum BchF revealed an integral transmembrane protein that was efficiently isolated by detergent solubilization. Recombinant C. tepidum BchC was purified as a soluble protein-NAD(+) complex. Substrate recognition of BchC was investigated using six artificial substrate molecules. Modification of the isocyclic E ring, omission of the central magnesium ion, zinc as an alternative metal ion, and a non-reduced B ring system were tolerated by BchC. According to this broadened in vitro activity, the chlorin 3-hydroxyethyl chlorophyllide a was newly identified as a natural substrate of BchC in a reconstituted pathway consisting of dark-operative protochlorophyllide oxidoreductase, BchF, and BchC. The established reaction sequence would allow for an additional new branching point for the synthesis of bacteriochlorophyll a. Biochemical and site-directed mutagenesis analyses revealed, in contrast to theoretical predictions, a zinc-independent BchC catalysis that requires NAD(+) as a cofactor. Based on these results, we are designating a new medium-chain dehydrogenase/reductase family (MDR057 BchC) as theoretically proposed from a recent bioinformatics analysis. |
| Databáze: | OpenAIRE |
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