title: A novel strategy of natural plant ferritin to protect DNA from oxidative damage during iron oxidation.
abstract: Plant ferritin is a naturally occurring heteropolymer in plastids, where Fe(2+) is oxidatively deposited into the protein. However, the effect of this process on the coexistence of DNA and plant ferritin in the plastids is unknown. To investigate this effect, we built a system in which various plant ferritins and DNA coexist, followed by treatment with ferrous ions under aerobic conditions. Interestingly, naturally occurring soybean seed ferritin (SSF), a heteropolymer with an H-1/H-2 ratio of 1 to 1 in the apo form, completely protected DNA from oxidative damage during iron oxidative deposition into protein, and a similar result was obtained with its recombinant form, but not with its homopolymeric counterparts, apo rH-1 and apo rH-2. We demonstrate that the difference in DNA protection between heteropolymeric and homopolymeric plant ferritins stems from their different strategies to control iron chemistry during the above oxidative process. For example, the detoxification reaction occurs only in the presence of apo heteropolymeric SSF (hSSF), thereby preventing the production of hydroxyl radicals. In contrast, hydroxyl radicals are apparently generated via the Fenton reaction when apo rH-1 or rH-2 is used instead of apo hSSF. Thus, a combination of H-1 and H-2 subunits in hSSF seems to impart a unique DNA-protective function to the protein, which was previously unrecognized. This new finding advances our understanding of the structure and function of ferritin and of the widespread occurrence of heteropolymeric plant ferritin in nature.
authors.affiliation: CAU & ACC Joint Laboratory of Space Food, College of Food Science and Nutritional Engineering, China Agricultural University, and Key Laboratory of Functional Dairy, Ministry of Education, Beijing 100083, China.
authors.forename: Xiayun
authors.initials: X
authors.lastname: Liao
authors.forename: Chenyan
authors.initials: C
authors.lastname: Lv
authors.forename: Xiuqing
authors.initials: X
authors.lastname: Zhang
authors.forename: Taro
authors.initials: T
authors.lastname: Masuda
authors.forename: Meiliang
authors.initials: M
authors.lastname: Li
authors.forename: Guanghua
authors.initials: G
authors.lastname: Zhao
mesh_terms: D001052:Apoferritins / Q000737:chemistry* / Q000378:metabolism; D004247:DNA / Q000737:chemistry*; D053938:DNA Fragmentation / Q000187:drug effects; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000494:pharmacology; D017665:Hydroxyl Radical; D007501:Iron / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010957:Plasmids / Q000737:chemistry; D018087:Plastids / Q000737:chemistry*; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013025:Glycine max / Q000737:chemistry*
chemical_list: D021122:Protein Subunits; D011994:Recombinant Proteins; D017665:Hydroxyl Radical; D004247:DNA; D001052:Apoferritins; D006861:Hydrogen Peroxide; D007501:Iron; D010100:Oxygen