Crystal Structure of Plant Ferritin Reveals a Novel Metal Binding Site That Functions as a Transit Site for Metal Transfer in Ferritin

Masuda, Taro; Goto, Fumiyuki; Yoshihara, Toshihiro; Mikami, Bunzo

doi:10.1074/jbc.m109.059790

Cited by 121 publications

(120 citation statements)

References 72 publications

(90 reference statements)

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“…The disparity in structure between plant and animal ferritins lies in EP (Masuda et al, 2010;Zhao, 2010), thus raising a question of whether EP is associated with PSF autodegradation. To address this question, EP-deleted PSF was prepared by incubating wild-type PSF with a commercially available protease, Alcalase 2.4L, based on a method reported earlier (Li et al, 2009a).…”

Section: Autodegradation Of Ep-involved Psfmentioning

confidence: 99%

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Protein Association and Dissociation Regulated by Extension Peptide: A Mode for Iron Control by Phytoferritin in Seeds

Yang

et al. 2010

Plant Physiology

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Most of the iron in legume seeds is stored in ferritin located in the amyloplast, which is used during seed germination. However, there is a lack of information on the regulation of iron by phytoferritin. In this study, soluble and insoluble forms of pea (Pisum sativum) seed ferritin (PSF) isolated from dried seeds were found to be identical 24-mer ferritins comprising H-1 and H-2 subunits. The insoluble form is favored at low pH, whereas the two forms reversibly interconvert in the pH range of 6.0 to 7.8, with an apparent pK a of 6.7. This phenomenon was not observed in animal ferritins, indicating that PSF is unique. The pH of the amyloplast was found to be approximately 6.0, thus facilitating PSF association, which is consistent with the role of PSF in long-term iron storage. Similar to previous studies, the results of this work showed that protein degradation occurs in purified PSF during storage, thus proving that phytoferritin also undergoes degradation during seedling germination. In contrast, no degradation was observed in animal ferritins, suggesting that this degradation of phytoferritin may be due to the extension peptide (EP), a specific domain found only in phytoferritin. Indeed, removal of EP from PSF significantly increased protein stability and prevented degradation under identical conditions while promoting protein dissociation. Correlated with such dissociation was a considerable increase in the rate of ascorbate-induced iron release from PSF at pH 6.0. Thus, phytoferritin may have facilitated the evolution of EP to enable it to regulate iron for storage or complement in seeds.

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Section: Autodegradation Of Ep-involved Psfmentioning

confidence: 99%

“…However, information regarding the regulation of phytoferritin iron in seeds is still lacking up to the present. Since EP represents the major structural difference between animal and plant ferritins (Masuda et al, 2010), this study focuses on determining whether EP domains participate in the regulation of phytoferritin iron.…”

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confidence: 99%

Protein Association and Dissociation Regulated by Extension Peptide: A Mode for Iron Control by Phytoferritin in Seeds

Yang

et al. 2010

Plant Physiology

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“…The putative secondary structure deduced from the three-dimensional structure of algal 26) and higher-plant ferritin 28) is shown in Fig. 2(A).…”

Section: Cdna Cloning Of Ferritin From P Yezoensis (Pyfer)mentioning

confidence: 99%

“…26,28) The EP region also presents in PyFer sequence in the downstream of putative TP region. Since the core region forming the 4-helix bundle is highly conserved among PyFer, UpFer, and other plant type ferritins, PyFer is also supposed to forms 4-helix bundle subunit, which assembles to spherical 24-mer.…”

Section: Cdna Cloning Of Ferritin From P Yezoensis (Pyfer)mentioning

confidence: 99%

The iron content and ferritin contribution in fresh, dried, and toasted nori, Pyropia yezoensis

Masuda

Yamamoto

Toyohara

2015

Bioscience, Biotechnology, and Biochemistry

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Iron is one of the essential trace elements for humans. In this study, the iron contents in fresh, dried, and toasted nori (Pyropia yezoensis) were analyzed. The mean iron content of fresh, dried, and toasted nori were 19.0, 22.6, and 26.2 mg/100 g (dry weight), respectively. These values were superior to other food of plant origin. Furthermore, most of the iron in nori was maintained during processing, such as washing, drying, and toasting. Then, the form of iron in fresh, dried, and toasted nori was analyzed. As a result, an iron storage protein ferritin contributed to iron storage in raw and dried nori, although the precise rate of its contribution is yet to be determined, while ferritin protein cage was degraded in the toasted nori. It is the first report that verified the ferritin contribution to iron storage in such edible macroalgae with commercial importance.

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“…In the case of soybean seed ferritin (SSF), each EP domain is composed of ϳ30 amino acid residues. The crystal structure of recombinant SSF shows that the EP is located on the exterior surface of protein and stabilizes the entire oligomeric conformation of phytoferritin by its interaction with a neighboring subunit on the shell surface (12). Recent studies of our group reveal the role of the EP during iron oxidative deposition in phytoferritin as the second binding and ferroxidase center that contributes to mineralization of the iron core at high iron loading of ferritin (Ͼ48 irons/shell) (13).…”

mentioning

confidence: 99%

Role of H-1 and H-2 Subunits of Soybean Seed Ferritin in Oxidative Deposition of Iron in Protein

Deng

Liao

Yang

et al. 2010

Journal of Biological Chemistry

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Naturally occurring phytoferritin is a heteropolymer consisting of two different H-type subunits, H-1 and H-2. Prior to this study, however, the function of the two subunits in oxidative deposition of iron in ferritin was unknown. The data show that, upon aerobic addition of 48 -200 Fe 2؉ /shell to apoferritin, iron oxidation occurs only at the diiron ferroxidase center of recombinant H1 (rH-1). In addition to the diiron ferroxidase mechanism, such oxidation is catalyzed by the extension peptide (a specific domain found in phytoferritin) of rH-2, because the H-1 subunit is able to remove Fe 3؉ from the center to the inner cavity better than the H-2 subunit. These findings support the idea that the H-1 and H-2 subunits play different roles in iron mineralization in protein. Interestingly, at medium iron loading (200 irons/shell), wild-type (WT) soybean seed ferritin (SSF) exhibits a stronger activity in catalyzing iron oxidation (1.10 ؎ 0.13 M iron/subunit/s) than rH-1 (0.59 ؎ 0.07 M iron/subunit/s) and rH-2 (0.48 ؎ 0.04 M iron/subunit/s), demonstrating that a synergistic interaction exists between the H-1 and H-2 subunits in SSF during iron mineralization. Such synergistic interaction becomes considerably stronger at high iron loading (400 irons/shell) as indicated by the observation that the iron oxidation activity of WT SSF is ϳ10 times larger than those of rH-1 and rH-2. This helps elucidate the widespread occurrence of heteropolymeric ferritins in plants.Iron and oxygen chemistry, in a variety of non-heme diiron proteins, has drawn considerable attention because of their various roles in reversible O 2 binding for respiration in hemerythrin, oxidation and desaturation of organic substrates in methane monooxygenase, R2 subunit of ribonucleotide reductase, stearoyl-acyl carrier protein ⌬-9 desaturase, as well as the detoxification and concentration of iron in Dps and ferritin (1-6). Diiron centers have similar structural motifs containing a combination of carboxylate and histidine ligands that either bind or bridge the two metal ions of the dinuclear active site. Although the dinuclear centers of the protein are very similar in structure, each of the proteins fulfills a different biological function that appears to be mediated by the nature of the first and second coordination sphere of the diiron center.Ferritins are a special class of diiron proteins that play a role in both iron housekeeping and iron detoxification. They are widely distributed in animals, plants, and bacteria (but not in yeast) and are typically composed of 24 similar or identical subunits assembled into a shell-like structure. In vertebrates, ferritins consist of two types of subunits, H and L, respectively. The two types have about 55% identity in amino acid sequence.

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Crystal Structure of Plant Ferritin Reveals a Novel Metal Binding Site That Functions as a Transit Site for Metal Transfer in Ferritin

Cited by 121 publications

References 72 publications

Protein Association and Dissociation Regulated by Extension Peptide: A Mode for Iron Control by Phytoferritin in Seeds

Protein Association and Dissociation Regulated by Extension Peptide: A Mode for Iron Control by Phytoferritin in Seeds

The iron content and ferritin contribution in fresh, dried, and toasted nori, Pyropia yezoensis

Role of H-1 and H-2 Subunits of Soybean Seed Ferritin in Oxidative Deposition of Iron in Protein

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