Iron‐Binding Properties of TTf, a Salt‐Induced Transferrin from the Alga<i>Dunaliella salina</i>

Schwarz, Michal; Zamir, Ada; Pick, Uri

doi:10.1081/pln-120024266

Cited by 10 publications

(12 citation statements)

References 22 publications

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“…The observation that D. salina cells contain prebound iron that is not removed by extensive washing is consistent with the high binding affinity of D. salina TTf for Fe 31 ions that we reported in previous studies None 0.9 6 0.2 (100) 3.8 6 0.6 (100) 2Bicarbonate 0.1 6 0.05 (10) 0.5 6 0.15 (13) (Fisher et al, 1998;Schwarz et al, 2003b Figure 3 and Table III, there is less than 10% exchange within 1 h at 4°C. The bound iron can be stripped off effectively by EDTA and, to a lesser extent, at acidic pH.…”

Section: Tightly Bound Iron Exchanges Slowly With Medium Fe 31supporting

confidence: 68%

“…Moreover, we found that isolated TTf from D. salina has very similar Fe 31 -binding parameters as intact cells and that dissociation of TTf from plasma membranes completely eliminated Fe-binding activity to TTf-deficient membranes (Schwarz et al, 2003b (Fisher et al, 1997(Fisher et al, , 1998. As shown in Table II, iron-deficient cells display a higher affinity for both iron and bicarbonate, suggesting changes in properties of the iron-binding sites.…”

Section: Dunaliella Cells Contain Externally Bound Ironmentioning

confidence: 73%

“…Under these conditions, .95% of the cell-associated iron was found to be externally bound to transferrins (bicarbonate dependent, EDTA sensitive). Plasma membrane vesicles were incubated for 1 h on ice with 59 Fe citrate in 50 mM Na-HEPES 8.0, 0.2 M KCl, and 5 mM NaHCO 3 and passed through semidry Sephadex G-50 columns to eliminate unbound 59 Fe as previously described (Schwarz et al, 2003b).…”

Section: Iron-binding Assaymentioning

confidence: 99%

“…A different high-affinity iron uptake mechanism was identified in the halotolerant alga D. salina, which is based on iron binding and internalization via a membrane-associated transferrin-like protein (TTf; Fisher et al, 1997Fisher et al, , 1998. In previous studies, we demonstrated that iron uptake and binding in D. salina resembles kinetic characteristics of animal transferrins and that the process consists of two distinct stages, binding and internalization of Fe 31 ions, which can be resolved by their different temperature dependence (Fisher et al, 1998;Schwarz, et al, 2003b). Iron deprivation or high salinity induces in D. salina a small stimulation of iron uptake that is correlated with the accumulation of TTf.…”

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Effects of Iron Deficiency on Iron Binding and Internalization into Acidic Vacuoles in Dunaliella salina

et al. 2007

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Uptake of iron in the halotolerant alga Dunaliella salina is mediated by a transferrin-like protein (TTf), which binds and internalizes Fe 31 ions. Recently, we found that iron deficiency induces a large enhancement of iron binding, which is associated with accumulation of three other plasma membrane proteins that associate with TTf. In this study, we characterized the kinetic properties of iron binding and internalization and identified the site of iron internalization. Iron deficiency induces a 4-fold increase in Fe binding, but only 50% enhancement in the rate of iron uptake and also increases the affinity for iron and bicarbonate, a coligand for iron binding. These results indicate that iron deprivation leads to accumulation and modification of iron-binding sites. Iron uptake in iron-sufficient cells is preceded by an apparent time lag, resulting from prebound iron, which can be eliminated by unloading iron-binding sites. Iron is tightly bound to surface-exposed sites and hardly exchanges with medium iron. All bound iron is subsequently internalized. Accumulation of iron inhibits further iron binding and internalization. The vacuolar inhibitor bafilomycin inhibits iron uptake and internalization. Internalized iron was localized by electron microscopy within vacuolar structures that were identified as acidic vacuoles. Iron internalization is accompanied by endocytosis of surface proteins into these acidic vacuoles. A novel kinetic mechanism for iron uptake is proposed, which includes two pools of bound/compartmentalized iron separated by a rate-limiting internalization stage. The major parameter that is modulated by iron deficiency is the iron-binding capacity. We propose that excessive iron binding in iron-deficient cells serves as a temporary reservoir for iron that is subsequently internalized. This mechanism is particularly suitable for organisms that are exposed to large fluctuations in iron availability.Iron is an essential element for survival for all living organisms, including photosynthetic organisms that have a special requirement for iron as a cofactor of multiple elements in their electron transport system. Because of its low solubility in aerobic solutions, iron is recognized as a major limiting factor for proliferation of plants and algae. To counterbalance iron limitation, photosynthetic organisms evolved efficient high-affinity iron uptake mechanisms that are induced under iron limitation. Two major mechanisms of iron acquisition studied in plants are based either on reduction of organic ferric iron chelates, via a membrane-associated ferrireductase (strategy I plants), or on release of phytosiderophores that bind ferric ions and introduce them into the cell via a special receptor (strategy II plants; Mori, 1999;Curie and Briat, 2003;

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Section: Tightly Bound Iron Exchanges Slowly With Medium Fe 31supporting

confidence: 68%

Section: Dunaliella Cells Contain Externally Bound Ironmentioning

confidence: 73%

Section: Iron-binding Assaymentioning

confidence: 99%

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Effects of Iron Deficiency on Iron Binding and Internalization into Acidic Vacuoles in Dunaliella salina

et al. 2007

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“…The iron-binding transferrin-like protein Ttf is a surface-associated protein that has been well characterized in our laboratory as a mediator of iron uptake (30,31).…”

Section: Functional Classification Of Identified Proteinsmentioning

confidence: 99%

Salt-induced Changes in the Plasma Membrane Proteome of the Halotolerant Alga Dunaliella salina as Revealed by Blue Native Gel Electrophoresis and Nano-LC-MS/MS Analysis

Katz

Waridel

Shevchenko

et al. 2007

Molecular & Cellular Proteomics

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The halotolerant alga Dunaliella salina is a recognized model photosynthetic organism for studying plant adaptation to high salinity. The adaptation mechanisms involve major changes in the proteome composition associated with energy metabolism and carbon and iron acquisition. To clarify the molecular basis for the remarkable resistance to high salt, we performed a comprehensive proteomics analysis of the plasma membrane. Plasma membrane proteins were recognized by tagging intact cells with a membrane-impermeable biotin derivative. Proteins were resolved by two-dimensional blue native/SDS-PAGE and identified by nano-LC-MS/MS. Of 55 identified proteins, about 60% were integral membrane or membraneassociated proteins. We identified novel surface coat proteins, lipid-metabolizing enzymes, a new family of membrane proteins of unknown function, ion transporters, small GTP-binding proteins, and heat shock proteins. The abundance of 20 protein spots increased and that of two protein spots decreased under high salt. The major salt-regulated proteins were implicated in protein and membrane structure stabilization and within signal transduction pathways. The migration profiles of native protein complexes on blue native gels revealed oligomerization or co-migration of major surface-exposed proteins, which may indicate mechanisms of stabilization at high salinity. Molecular & Cellular Proteomics 6:1459 -1472, 2007.The halotolerant alga Dunaliella salina uses a unique osmoregulatory mechanism and is able to proliferate in environments with extreme salt content (1). This is achieved through remarkable changes in metabolism and ion transport brought about by up-regulation or down-regulation of multiple enzymes and membrane proteins. Elucidation of the molecular basis for this remarkable adaptation might provide tools to improve the resistance of crop plants to the progressive salinization of soils, which is already a major limitation for agricultural productivity worldwide. By characterizing the changes in the soluble subproteome of D. salina, we demonstrated previously that the alga responds to hypersaline conditions by up-regulating key enzymes in photosynthetic CO 2 fixation and in energy metabolism that divert carbon metabolism to massive synthesis of glycerol, the osmotic element in Dunaliella (2).Salinity stress destabilizes biological membranes and affects the solubility of many essential substrates and ions (3). Adaptation to salinity stress might also alter the composition and organization of the membrane proteome associated with the stabilization and enhancement of ion transporters. Early studies revealed the accumulation of two carbonic anhydrases, dCAI 1 and dCAII (4, 5), and a transferrin-like protein (6) that presumably compensated the impaired availability of bicarbonate and iron under high salt. Salt-induced changes in organellar membranes, such as the expression of ER fatty acid elongase, were also reported (7). High salinity also affects sodium transport (8), lipid organization (9, 10), and activation of PM pr...

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Spin States of 1D Iron(II) Coordination Polymers with Redox Active TTF(py)₂ as Bridging Ligand

Schönfeld

Hörner

Heinemann

et al. 2020

Zeitschrift anorg allge chemie

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In this manuscript, we report the solvent‐dependent synthesis of 1D coordination polymers derived from two planar N2O2‐coordinate iron(II) complexes FeL1 and FeL2, which incorporate TTF(py)2 as a bridging bis‐monodentate ligand. The obtained 1D polymers were characterized through elemental analysis, Mössbauer spectroscopy, single crystal structure analysis for 2a·2 DMF, magnetic susceptibility measurements, X‐ray powder diffraction, cyclic voltammetry and diffuse reflectance spectroscopy, supplemented by DFT computation. The results revealed additive electronic properties of the sub‐units FeL and TTF(py)2 with only minor mutual influence. Intriguingly however, the solvent‐of‐synthesis is found to be a steering factor of the magnetic spin crossover properties of the resulting materials, yielding divergent behavior if obtained from DMF, MeCN or EtOH. This becomes strikingly evident for the magnetic properties of the DMF‐derived polymer which is found trapped in the low‐spin state in the single crystal 2a· 2 DMF, but shows a gradual spin crossover if all solvent is removed.

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Iron‐Binding Properties of TTf, a Salt‐Induced Transferrin from the AlgaDunaliella salina

Cited by 10 publications

References 22 publications

Effects of Iron Deficiency on Iron Binding and Internalization into Acidic Vacuoles in Dunaliella salina

Effects of Iron Deficiency on Iron Binding and Internalization into Acidic Vacuoles in Dunaliella salina

Salt-induced Changes in the Plasma Membrane Proteome of the Halotolerant Alga Dunaliella salina as Revealed by Blue Native Gel Electrophoresis and Nano-LC-MS/MS Analysis

Spin States of 1D Iron(II) Coordination Polymers with Redox Active TTF(py)₂ as Bridging Ligand

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Iron‐Binding Properties of TTf, a Salt‐Induced Transferrin from the AlgaDunaliella salina

Cited by 10 publications

References 22 publications

Effects of Iron Deficiency on Iron Binding and Internalization into Acidic Vacuoles in Dunaliella salina

Effects of Iron Deficiency on Iron Binding and Internalization into Acidic Vacuoles in Dunaliella salina

Salt-induced Changes in the Plasma Membrane Proteome of the Halotolerant Alga Dunaliella salina as Revealed by Blue Native Gel Electrophoresis and Nano-LC-MS/MS Analysis

Spin States of 1D Iron(II) Coordination Polymers with Redox Active TTF(py)2 as Bridging Ligand

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Product

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Spin States of 1D Iron(II) Coordination Polymers with Redox Active TTF(py)₂ as Bridging Ligand