Functional Genes Found for Three Different Plant Ferritin Subunits in the Legume, Vigna unguiculata

Wicks, Ronald E.; Entsch, Barrie

doi:10.1006/bbrc.1993.1487

Cited by 26 publications

(24 citation statements)

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“…Consistent with this idea, two other soybean ferritin subunits, H-3 and H-4, have distinct EP domains from their analogues H-1 and H-2, and homopolymer rH-3 exhibits lower iron incorporation activity as compared with rH-1 and rH-2 (18). Further support for this proposal comes from previous studies showing that cowpea leaf ferritin (39), maize ferritin (40), and pea seed ferritin (17) consist of two or more different subunits, which contain specific EP domains at the N-terminal extremity.…”

Section: Discussionmentioning

confidence: 58%

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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Section: Discussionmentioning

confidence: 58%

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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“…At a structural level, it is consistent with the absence of an iron responsive element (IRE), responsible for the iron-dependent translational regulation of animal ferritin messenger RNA (mRNA), in all plant ferritin mRNA and genes characterised so far [9]. However, all the members of the plant ferritin complementary DNA (cDNA) and gene family have not yet been fully characterised [10], and it cannot be ruled out that additional structural features remain to be discovered for this class of plant genes.…”

Section: Plant Ferritin Genes and Protein Structurementioning

confidence: 95%

Regulation of plant ferritin synthesis: how and why

Briat¹,

Lobréaux²,

Grignon³

et al. 1999

Cellular and Molecular Life Sciences (CMLS)

125

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Plant ferritins are key iron-storage proteins that share important structural and functional similarities with animal ferritins. However, specific features characterize plant ferritins, among which are plastid cellular localization and transcriptional regulation by iron. Ferritin synthesis is developmentally and environmentally controlled, in part through the differential expression of the various members of a small gene family. Furthermore, a strict requirement for plant ferritin synthesis regulation is attested to by alterations of the photosynthetic apparatus and of iron homeostasis in transgenic tobaccos overexpressing these proteins. Plant ferritin gene regulation appears to consist of a complex interplay of transcriptional and posttranscriptional mechanisms, involving cellular relays such as plant hormones, oxidative steps and Ser/Thr phosphatase.

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“…Recently, multiple copies of the ferritin gene were identified from various plant species (22)(23)(24)(25)(26)(27)(28)(29)(30). It has been suggested that their expression was differentially regulated via various environmental stresses or metal overload (25,(31)(32)(33)(34)(35)(36), and are sometimes subjected to different types of processing (26,30).…”

mentioning

confidence: 99%

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

Masuda

Goto

Yoshihara

et al. 2010

Journal of Biological Chemistry

122

116

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Ferritins are important iron storage and detoxification proteins that are widely distributed in living kingdoms. Because plant ferritin possesses both a ferroxidase site and a ferrihydrite nucleation site, it is a suitable model for studying the mechanism of iron storage in ferritin. This article presents for the first time the crystal structure of a plant ferritin from soybean at 1.8-Å resolution. The soybean ferritin 4 (SFER4) had a high structural similarity to vertebrate ferritin, except for the N-terminal extension region, the C-terminal short helix E, and the end of the BC-loop. Similar to the crystal structures of other ferritins, metal binding sites were observed in the iron entry channel, ferroxidase center, and nucleation site of SFER4. In addition to these conventional sites, a novel metal binding site was discovered intermediate between the iron entry channel and the ferroxidase site. This site was coordinated by the acidic side chain of Glu 173 and carbonyl oxygen of Thr 168 , which correspond, respectively, to Glu 140 and Thr 135 of human H chain ferritin according to their sequences. A comparison of the ferroxidase activities of the native and the E173A mutant of SFER4 clearly showed a delay in the iron oxidation rate of the mutant. This indicated that the glutamate residue functions as a transit site of iron from the 3-fold entry channel to the ferroxidase site, which may be universal among ferritins.

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Functional Genes Found for Three Different Plant Ferritin Subunits in the Legume, Vigna unguiculata

Cited by 26 publications

References 0 publications

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

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

Regulation of plant ferritin synthesis: how and why

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

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