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[Objective] This study aims to validate the functions of two ferritin-encoding genes: bacterioferritin (Bfr)-encoding gene (atu2771) and DNA-binding protein from starved cells (Dps)-encoding gene (atu2477), in Agrobacterium fabrum, to determine the open reading frame (ORF) of the Bfr-encoding gene, to investigate the effects of terminal fusion, heme group, and key residues on the function and self-assembly of A. fabrum Bfr, and to explore the potential applications of the two ferritin nano-cages. [Methods] We re-introduced the two ferritin-encoding genes into the ferritin-deficient mutants of A. fabrum respectively via plasmids to verify if the re-introduction could complement the ferritins of the ferritin-deficient mutants and thus validate the functions of the two genes. Native PAGE was employed to separate the ferritins in the crude extract of A. fabrum and potassium ferrocyanide (an iron-specific staining reagent) was used to stain the ferritins. Various peptides or protein were fused to the termini of two ferritins to test if the terminal fusion would affect the functions and self-assembly of the two ferritins. Site-directed mutation was then employed to test the effects of the key residue and heme group on the function and self-assembly of Bfr. [Results] Iron-specific staining on the ferritins separated by native PAGE showed that the Bfr-encoding gene expressed Bfr in all the tested A. fabrum strains, whereas the Dps-encoding gene expressed Dps in none of the tested A. fabrum strains. Complementary experiment with two different Bfr-encoding ORFs (encoding 161 residues and 169 residues) showed that Bfr in the wild type was encoded by the ORF encoding 161 residues. The results demonstrated that terminal fusions with different peptides or protein influenced but did not abolish the function and self-assembly of Bfr. The substitution of Met60, which was predicted to chelate the iron of heme, indicated that heme affected the function and self-assembly of Bfr but was not indispensable. [Conclusion] A. fabrum utilizes Bfr to store iron. The ORF of the Bfr-encoding gene utilizes UUG (a rare start code) as its start code and encodes a Bfr composed of 161 residues. The Dps-encoding gene of A. fabrum expressed in none of the tested conditions. The structures of both Bfr and Dps of A. fabrum are stable enough to withstand the terminal fusion with various peptides or protein, suggesting that both Bfr and Dps nano-cages demonstrate great promise for biotechnological applications.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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