Recombinant Chlorobium phaeobacteroides Lipoyl synthase (lipA)
Description
Molecular Function and Biological Role
Lipoyl synthase (LipA) catalyzes the final step in de novo lipoic acid biosynthesis by inserting two sulfur atoms into octanoyl-ACP to form lipoyl-lysine, a cofactor for pyruvate dehydrogenase and other enzyme complexes . Chlorobium phaeobacteroides LipA shares structural and catalytic features with homologs in Escherichia coli and plants, including:
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Iron-sulfur clusters: Two [4Fe–4S] clusters (a radical SAM cluster and an auxiliary cluster) required for sulfur transfer .
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Mechanism: Utilizes S-adenosylmethionine (SAM) to generate 5-deoxyadenosyl radicals, enabling sulfur abstraction from the auxiliary cluster for lipoic acid synthesis .
Heterologous Production and Expression Systems
Recombinant C. phaeobacteroides LipA is produced using multiple expression platforms, as detailed in commercial and research-grade systems :
| Production System | Features |
|---|---|
| E. coli | Standard host for high-yield protein expression; compatible with affinity tags. |
| Baculovirus | Eukaryotic insect cell system for post-translational modifications. |
| Mammalian Cells | Suitable for humanized glycosylation studies. |
| In Vivo Biotinylation | Enables site-specific biotin tagging for pull-down assays in E. coli. |
Comparative Analysis with Bacterial LipA Homologs
C. phaeobacteroides LipA shares functional parallels with homologs in E. coli and pathogens like Pasteurella multocida, though its ecological role in a nonpathogenic, photosynthetic bacterium remains enigmatic . Key distinctions include:
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Evolutionary divergence: Green sulfur bacteria (Chlorobi) diverged from Proteobacteria ~2.5–3 billion years ago, suggesting ancient conservation of lipoic acid biosynthesis pathways .
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Gene transfer: Horizontal gene transfer is unlikely due to ecological niche differences, implying vertical inheritance of LipA in Chlorobi .
Unresolved Questions and Future Directions
Product Specs
Target Background
KEGG: cph:Cpha266_1277
STRING: 290317.Cpha266_1277
