Recombinant Ferrochelatase 2 (hemH2)
Description
Definition and Nomenclature
Recombinant Ferrochelatase 2 (hemH2) refers to a genetically engineered version of ferrochelatase isoform 2 (FC2), a chloroplast-localized enzyme critical for heme biosynthesis in plants. It catalyzes the insertion of ferrous iron into protoporphyrin IX, forming protoheme, the precursor for chlorophyll and heme-dependent proteins in plastids . The recombinant form is produced via heterologous expression in host systems such as E. coli, yeast, or baculovirus-infected cells .
Chloroplast Heme Allocation
FC2 primarily supplies heme for photosynthetic proteins, including:
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Cytochrome b₆f complex: Critical for light-driven electron transport .
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Photosystem I/II reaction centers: Structural and functional integrity depends on FC2-derived heme .
Experimental Evidence:
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fc2-2 mutants exhibit ~30% reduction in total heme and impaired cytochrome b₆f assembly .
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Loss of FC2 disrupts LHCII-PSII supercomplex formation, altering chlorophyll a/b ratios .
Regulation of Tetrapyrrole Biosynthesis
FC2 interacts with the GluTR-inactivation complex (PORB-FLU-GluTR) to:
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Stabilize POR (NADPH-dependent protochlorophyllide oxidoreductase).
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Suppress ALA synthesis by modulating HEMA1 (glutamyl-tRNA reductase) activity .
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Prevent protochlorophyllide accumulation, mitigating photodynamic damage .
Key Interaction Partners:
Recombinant Expression Systems
FC2 is typically produced via:
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Heterologous overexpression in E. coli or yeast, often co-expressed with δ-aminolevulinic acid (δ-ALA) to ensure heme precursor availability .
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Baculovirus/mammalian systems for post-translational modifications, though less common for plant FC2 .
Optimal Conditions:
Applications in Research
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Chloroplast Heme Biology:
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Protein Engineering:
Tissue-Specific Functions
| Mutant | Phenotype | Heme Deficiency |
|---|---|---|
| fc2-2 | Pale cotyledons, reduced cytochrome b₆f, delayed greening | ~30% of wild-type |
| fc1-1 | Embryo lethality, compromised root development | Undetectable in seedlings |
| fc1-1 fc2-2 | Severe growth arrest, infertility | Severe global heme loss |
Stress Responses
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Flg22-induced defense: FC2 does not directly contribute to stress-responsive peroxidase activity, which relies on FC1 .
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Lignin accumulation: FC2-independent, suggesting redundant heme pathways in defense .
Comparative Analysis of Ferrochelatase Isoforms
| Feature | FC2 | FC1 |
|---|---|---|
| Tissue Expression | Photosynthetic tissues (leaf, cotyledon) | Roots, flowers, stress-responsive |
| Heme Allocation | Chloroplast proteins (cytochromes, LHC) | Extraplastidic hemoproteins (peroxidases) |
| Stress Induction | Repressed by flg22 | Induced by flg22 |
| Evolutionary Origin | Chloroplast-targeted | Housekeeping, cytosolic/extraplastidic |
Product Specs
Target Background
Ferrochelatase 2 (hemH2) participates in coproporphyrin-dependent heme b biosynthesis. Its function is to catalyze the insertion of ferrous iron into coproporphyrin III, yielding Fe-coproporphyrin III.
KEGG: ban:BA_1158
STRING: 260799.BAS1075
