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Borko V, Friganović T, Weitner T. Glycoproteomics meets thermodynamics: A calorimetric study of the effect of sialylation and synergistic anion on the binding of iron to human serum transferrin. J Inorg Biochem 2023; 244:112207. [PMID: 37054508 DOI: 10.1016/j.jinorgbio.2023.112207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 03/20/2023] [Accepted: 04/02/2023] [Indexed: 04/09/2023]
Abstract
The thermodynamic parameters for the binding of ferric ions to human serum transferrin (hTf) as the major mediator of iron transport in blood plasma were determined by isothermal titration calorimetry in the presence of carbonate and oxalate as synergistic anions at pH 7.4. The results indicate that the binding of ferric ions to the two binding sites of hTf is driven both enthalpically and entropically in a lobe-dependent manner: binding to the C-site is mainly enthalpically driven, whereas binding to the N-site is mainly entropically driven. Lower sialic acid content of hTf leads to more exothermic apparent binding enthalpies for both lobes, while the increased apparent binding constants for both sites were found in the presence of carbonate. Sialylation also unequally affected the heat change rates for both sites only in the presence of carbonate, but not in the presence of oxalate. Overall, the results suggest that the desialylated hTf has a higher iron sequestering ability, which may have implications for iron metabolism.
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Kumar R, Sharma D, Kumar N, Kumari B, Kumar S, Kumar R. Substitution of carbonate by non-physiological synergistic anion modulates the stability and iron release kinetics of serum transferrin. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2023; 1871:140856. [PMID: 36252939 DOI: 10.1016/j.bbapap.2022.140856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 09/26/2022] [Accepted: 10/04/2022] [Indexed: 11/06/2022]
Abstract
Serum transferrin (sTf) is a bi-lobal protein. Each lobe of sTf binds one Fe3+ ion in the presence of a synergistic anion. Physiologically, carbonate is the main synergistic anion but other anions such as oxalate, malonate, glycolate, maleate, glycine, etc. can substitute for carbonate in vitro. The present work provides the possible pathways by which the substitution of carbonate with oxalate affects the structural, kinetic, thermodynamic, and functional properties of blood plasma sTf. Analysis of equilibrium experiments measuring iron release and structural unfolding of carbonate and oxalate bound diferric-sTf (Fe2sTf) as a function of pH, urea concentration, and temperature reveal that the structural and iron-centers stability of Fe2sTf increase by substitution of carbonate with oxalate. Analysis of isothermal titration calorimetry (ITC) scans showed that the affinity of Fe3+ with apo-sTf is enhanced by substituting carbonate with oxalate. Analysis of kinetic and thermodynamic parameters measured for the iron release from the carbonate and oxalate bound monoferric-N-lobe of sTf (FeNsTf) and Fe2sTf at pH 7.4 and pH 5.6 reveals that the substitution of carbonate with oxalate inhibits/retards the iron release via increasing the enthalpic barriers.
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Affiliation(s)
- Rajesh Kumar
- School of Chemistry and Biochemistry, Thapar University, Patiala 147004, India
| | - Deepak Sharma
- Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh, India
| | - Navinder Kumar
- Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh, India
| | - Beeta Kumari
- Deparment of Chemistry, School of Basic Sciences, Central University of Punjab, Ghudda, Bathinda 151401, India
| | - Sanjeev Kumar
- Deparment of Chemistry, School of Basic Sciences, Central University of Punjab, Ghudda, Bathinda 151401, India
| | - Rajesh Kumar
- Deparment of Chemistry, School of Basic Sciences, Central University of Punjab, Ghudda, Bathinda 151401, India; School of Chemistry and Biochemistry, Thapar University, Patiala 147004, India.
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3
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Weber JJ, Kashipathy MM, Battaile KP, Go E, Desaire H, Kanost MR, Lovell S, Gorman MJ. Structural insight into the novel iron-coordination and domain interactions of transferrin-1 from a model insect, Manduca sexta. Protein Sci 2021; 30:408-422. [PMID: 33197096 PMCID: PMC7784759 DOI: 10.1002/pro.3999] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 11/11/2020] [Accepted: 11/13/2020] [Indexed: 11/07/2022]
Abstract
Transferrins function in iron sequestration and iron transport by binding iron tightly and reversibly. Vertebrate transferrins coordinate iron through interactions with two tyrosines, an aspartate, a histidine, and a carbonate anion, and conformational changes that occur upon iron binding and release have been described. Much less is known about the structure and functions of insect transferrin-1 (Tsf1), which is present in hemolymph and influences iron homeostasis mostly by unknown mechanisms. Amino acid sequence and biochemical analyses have suggested that iron coordination by Tsf1 differs from that of the vertebrate transferrins. Here we report the first crystal structure (2.05 Å resolution) of an insect transferrin. Manduca sexta (MsTsf1) in the holo form exhibits a bilobal fold similar to that of vertebrate transferrins, but its carboxyl-lobe adopts a novel orientation and contacts with the amino-lobe. The structure revealed coordination of a single Fe3+ ion in the amino-lobe through Tyr90, Tyr204, and two carbonate anions. One carbonate anion is buried near the ferric ion and is coordinated by four residues, whereas the other carbonate anion is solvent exposed and coordinated by Asn121. Notably, these residues are highly conserved in Tsf1 orthologs. Docking analysis suggested that the solvent exposed carbonate position is capable of binding alternative anions. These findings provide a structural basis for understanding Tsf1 function in iron sequestration and transport in insects as well as insight into the similarities and differences in iron homeostasis between insects and humans.
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Affiliation(s)
- Jacob J. Weber
- Department of Biochemistry and Molecular BiophysicsKansas State UniversityManhattanKansasUSA
| | - Maithri M. Kashipathy
- Protein Structure Laboratory, Del Shankel Structural Biology CenterUniversity of KansasLawrenceKansasUSA
| | | | - Eden Go
- Department of ChemistryUniversity of KansasLawrenceKansasUSA
| | - Heather Desaire
- Department of ChemistryUniversity of KansasLawrenceKansasUSA
| | - Michael R. Kanost
- Department of Biochemistry and Molecular BiophysicsKansas State UniversityManhattanKansasUSA
| | - Scott Lovell
- Protein Structure Laboratory, Del Shankel Structural Biology CenterUniversity of KansasLawrenceKansasUSA
| | - Maureen J. Gorman
- Department of Biochemistry and Molecular BiophysicsKansas State UniversityManhattanKansasUSA
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4
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Nakazawa S, Kanno T, Sugisaki K, Kameya H, Matsui M, Ukai M, Sato K, Takui T. Fe-transferrins or their homologues in ex-vivo mushrooms as identified by ESR spectroscopy and quantum chemical calculations: A full spin-Hamiltonian approach for the ferric sextet state with intermediate zero-field splitting parameters. Food Chem 2018; 266:24-30. [PMID: 30381181 DOI: 10.1016/j.foodchem.2018.05.092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 04/26/2018] [Accepted: 05/21/2018] [Indexed: 10/16/2022]
Abstract
Fe-transferrins/their homologues in ex-vivo mushrooms were identified by ESR spectroscopy at liquid helium temperature, 4 K. The ESR fine-structure signals from Grifola frondosa were analyzed by spectral simulation with a full spin-Hamiltonian approach, determining the spin Hamiltonian parameters of the ferric iron species bound in the biological environment: S = 5/2, g = (2.045, 2.01, 2.235), |D| = 0.28 cm-1, |E/D| = 0.05. The zero-field splitting (ZFS) parameters, D- and E-values, are very close to the reported values, |D| = 0.25 cm-1 and |E/D| = 0.06, for an Fe-transferrin with oxalate anion, and to |D| = 0.25 cm-1 and |E/D| = 0.04 for one with malonate anion in human sera, suggesting that the Fe3+ species are from Fe-transferrins or their homologues. Quantum chemical calculations of the ZFS tensors for Fe-transferrins were carried out. Fe-transferrins/homologues have been identified for all the mushrooms under study, suggesting that such Fe3+ enzymes are widely distributed in mushrooms.
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Affiliation(s)
- Shigeaki Nakazawa
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan.
| | - Tomomi Kanno
- Department of Health and Nutritional Sciences, Faculty of Health and Medical Sciences, Aichi Shukutoku University, Aichi 480-1197, Japan.
| | - Kenji Sugisaki
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
| | - Hiromi Kameya
- Food Research Institute, National Agriculture and Food Research Organization, Ibaraki 305-8642, Japan
| | - Miki Matsui
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
| | - Mitsuko Ukai
- Hakodate Campus, Hokkaido University of Education, Hakodate 040-8567, Japan
| | - Kazunobu Sato
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
| | - Takeji Takui
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan.
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5
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Ghanbari Z, Housaindokht M, Bozorgmehr M, Izadyar M. Effects of synergistic and non-synergistic anions on the iron binding site from serum transferrin: A molecular dynamic simulation analysis. J Mol Graph Model 2017; 78:176-186. [DOI: 10.1016/j.jmgm.2017.10.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 10/12/2017] [Accepted: 10/16/2017] [Indexed: 11/15/2022]
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6
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Conformational control of human transferrin covalently anchored to carbon-coated iron nanoparticles in presence of a magnetic field. Acta Biomater 2016; 45:367-374. [PMID: 27581396 DOI: 10.1016/j.actbio.2016.08.047] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 08/18/2016] [Accepted: 08/24/2016] [Indexed: 01/05/2023]
Abstract
The control of the interactions of proteins with the support matrix plays a key role in medicine, drug delivery systems and diagnostics. Herein, we report that covalent anchoring of human transferrin to carbon-coated iron magnetic nanoparticles functionalized with carboxylic groups (Fe@C-COOH Nps) in the presence of magnetic field results in its conformational integrity and electroactivity. We have found that, the direct contact of human transferrin with Fe@C-COOH Nps does not lead to release of iron and in consequence to the irreversible conformational changes of the protein. Moreover, the examination of the direct electron transfer between Tf molecules from the conjugate and the electrode surface was possible. The quartz crystal microbalance with dissipation (QCM-D)- and thermogravimetric data (TGA) showed that under such conditions, in addition to a monolayer, an adlayer of the protein can be formed on Fe@C-COOH Nps at constant pH. STATEMENT OF SIGNIFICANCE To our best knowledge this is the first paper that reports on covalent anchoring of human transferrin (Tf) to carbon-coated iron magnetic nanoparticles functionalized with carboxylic groups (Fe@C-COOH Nps) in the presence of magnetic field, which results in its conformational integrity and electroactivity. We showed that it is possible to attach, without changing pH, more than one single layer of transferrin to the Fe@C-COOH Nps. This is a very rare phenomenon in the case of proteins. We proved, using various experimental techniques, that the proposed methodology does not lead to release of iron from Tf molecules, what was the major problem so far. We believe that this finding opens new possibilities in targeting drug delivery systems and medical diagnostics.
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Sethumadhavan S, Whitsett J, Bennett B, Ionova IA, Pieper GM, Vasquez-Vivar J. Increasing tetrahydrobiopterin in cardiomyocytes adversely affects cardiac redox state and mitochondrial function independently of changes in NO production. Free Radic Biol Med 2016; 93:1-11. [PMID: 26826575 PMCID: PMC5498285 DOI: 10.1016/j.freeradbiomed.2016.01.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 12/31/2015] [Accepted: 01/25/2016] [Indexed: 02/07/2023]
Abstract
Tetrahydrobiopterin (BH4) represents a potential strategy for the treatment of cardiac remodeling, fibrosis and/or diastolic dysfunction. The effects of oral treatment with BH4 (Sapropterin™ or Kuvan™) are however dose-limiting with high dose negating functional improvements. Cardiomyocyte-specific overexpression of GTP cyclohydrolase I (mGCH) increases BH4 several-fold in the heart. Using this model, we aimed to establish the cardiomyocyte-specific responses to high levels of BH4. Quantification of BH4 and BH2 in mGCH transgenic hearts showed age-based variations in BH4:BH2 ratios. Hearts of mice (<6 months) have lower BH4:BH2 ratios than hearts of older mice while both GTPCH activity and tissue ascorbate levels were higher in hearts of young than older mice. No evident changes in nitric oxide (NO) production assessed by nitrite and endogenous iron-nitrosyl complexes were detected in any of the age groups. Increased BH4 production in cardiomyocytes resulted in a significant loss of mitochondrial function. Diminished oxygen consumption and reserve capacity was verified in mitochondria isolated from hearts of 12-month old compared to 3-month old mice, even though at 12 months an improved BH4:BH2 ratio is established. Accumulation of 4-hydroxynonenal (4-HNE) and decreased glutathione levels were found in the mGCH hearts and isolated mitochondria. Taken together, our results indicate that the ratio of BH4:BH2 does not predict changes in neither NO levels nor cellular redox state in the heart. The BH4 oxidation essentially limits the capacity of cardiomyocytes to reduce oxidant stress. Cardiomyocyte with chronically high levels of BH4 show a significant decline in redox state and mitochondrial function.
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Affiliation(s)
- Savitha Sethumadhavan
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Jennifer Whitsett
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Brian Bennett
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; Department of Physics, Marquette University, Milwaukee, 1250 W Wisconsin Ave, Milwaukee, WI 53233, USA
| | - Irina A Ionova
- Department of Surgery Medicine, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Galen M Pieper
- Department of Surgery Medicine, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Jeannette Vasquez-Vivar
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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8
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Moderate conformational impact of citrate on ovotransferrin considerably increases its capacity to self-assemble at the interface. J Colloid Interface Sci 2015; 437:219-226. [DOI: 10.1016/j.jcis.2014.09.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 09/12/2014] [Accepted: 09/15/2014] [Indexed: 11/30/2022]
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9
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Exploring the Fe(III) binding sites of human serum transferrin with EPR at 275 GHz. J Biol Inorg Chem 2014; 20:487-96. [DOI: 10.1007/s00775-014-1229-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 12/10/2014] [Indexed: 10/24/2022]
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10
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Wong BX, Ayton S, Lam LQ, Lei P, Adlard PA, Bush AI, Duce JA. A comparison of ceruloplasmin to biological polyanions in promoting the oxidation of Fe2+ under physiologically relevant conditions. Biochim Biophys Acta Gen Subj 2014; 1840:3299-310. [DOI: 10.1016/j.bbagen.2014.08.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 07/31/2014] [Accepted: 08/14/2014] [Indexed: 12/31/2022]
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11
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Harris WR. Anion binding properties of the transferrins. Implications for function. Biochim Biophys Acta Gen Subj 2011; 1820:348-61. [PMID: 21846492 DOI: 10.1016/j.bbagen.2011.07.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 07/25/2011] [Accepted: 07/28/2011] [Indexed: 10/17/2022]
Abstract
BACKGROUND Since the transferrins have been defined by the highly cooperative binding of Fe(3+) and a carbonate anion to form an Fe-CO(3)-Tf ternary complex, the focus has been on synergistic anion binding. However, there are other types of anion binding with both apotransferrin and diferric transferrin that affect metal binding and release. SCOPE OF REVIEW This review covers the binding of anions to the apoprotein, as well as the formation and structure of Fe-anion-transferrin ternary complexes. It also covers interactions between ferric transferrin and non-synergistic anions that appear to be important in vivo. GENERAL SIGNIFICANCE The interaction of anions with apotransferrin can alter the effective metal binding constants, which can affect the transport of metal ions in serum. These interactions also play a role in iron release under physiological conditions. MAJOR CONCLUSIONS Apotransferrin binds a variety of anions with no special selectivity for carbonate. The selectivity for carbonate as a synergistic anion is associated with the iron binding reaction. Conformational changes in the binding of the synergistic carbonate and competition from non-synergistic anions both play a role in intracellular iron release. Anion competition also occurs in serum and reduces the effective metal binding affinity of Tf. Lastly, anions bind to allosteric sites (KISAB sites) on diferric transferrin and alter the rates of iron release. The KISAB sites have not been well-characterized, but kinetic studies on iron release from mutant transferrins indicate that there are likely to be multiple KISAB sites for each lobe of transferrin. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
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Affiliation(s)
- Wesley R Harris
- Department of Chemistry & Biochemistry, University of Missouri-St. Louis, St. Louis, MO 63121, USA.
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12
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Sharma R, Harris WR. Allosteric effects of sulfonate anions on the rates of iron release from serum transferrin. J Inorg Biochem 2011; 105:1148-55. [PMID: 21708099 DOI: 10.1016/j.jinorgbio.2011.05.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 05/27/2011] [Accepted: 05/31/2011] [Indexed: 11/30/2022]
Abstract
Serum transferrin is the protein that transports ferric ion through the bloodstream and is thus a potential target for iron chelation therapy. However, the release of iron from transferrin to low-molecular-weight chelating agents is usually quite slow. Thus a better understanding of the mechanism for iron release is important to assist in the design of more effective agents for iron removal. This paper describes the effect of sulfonate anions on the rates of iron removal from C-terminal monoferric transferrin by acetohydroxamic acid, deferiprone, nitrilotriacetic acid (NTA), and diethylenetriaminepentaacetic acid at 25°C in 0.1M N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (Hepes) buffer at pH 7.4. These ligands remove iron via a combination of pathways that show saturation and first order dependence on the ligand concentration. The kinetic effects of the anions methanesulfonate, methylenedisulfonate, and ethylenedisulfonate were evaluated. All these anions increase the overall rates of iron release, presumably by binding to an allosteric anion binding site on the protein. The two disulfonates produce a larger acceleration in iron release than the monosulfonate. More detailed studies using methylenedisulfonate show that this anion accelerates the rate of iron release via the saturation pathway. The addition of methylenedisulfonate results in the appearance of a large saturation pathway for iron release by NTA, which otherwise removes iron by a simple first-order process. The sulfonate group was selected for these studies because it represents an anionic functional group that can be covalently linked to a therapeutic ligand to accelerate iron release in vivo. The current studies indicate that the binding of the sulfonates to the allosteric site on the protein is quite weak, so that one would not expect a significant acceleration in iron release at clinically relevant ligand concentrations.
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Affiliation(s)
- Rashmi Sharma
- Department of Chemistry & Biochemistry, University of Missouri-St. Louis, St. Louis, MO 63121, USA
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13
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Byrne SL, Steere AN, Chasteen ND, Mason AB. Identification of a kinetically significant anion binding (KISAB) site in the N-lobe of human serum transferrin. Biochemistry 2010; 49:4200-7. [PMID: 20397659 DOI: 10.1021/bi1003519] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human serum transferrin (hTF) binds two ferric iron ions which are delivered to cells in a transferrin receptor (TFR) mediated process. Critical to the delivery of iron to cells is the binding of hTF to the TFR and the efficient release of iron orchestrated by the interaction. Within the endosome, iron release from hTF is also aided by lower pH, the presence of anions, and a chelator yet to be identified. We have recently shown that three of the four residues comprising a loop in the N-lobe (Pro142, Lys144, and Pro145) are critical to the high-affinity interaction of hTF with the TFR. In contrast, Arg143 in this loop does not participate in the binding isotherm. In the current study, the kinetics of iron release from alanine mutants of each of these four residues (placed into both diferric and monoferric N-lobe backgrounds) have been determined +/- the TFR. The R143A mutation greatly retards the rate of iron release from the N-lobe in the absence of the TFR but has considerably less of an effect in its presence. Our data definitively show that Arg143 serves as a kinetically significant anion binding (KISAB) site that is, by definition, sensitive to salt concentration and critical to the conformational change necessary to induce iron release from the N-lobe of hTF (in the absence of the TFR). This is the first identification of an authentic KISAB site in the N-lobe of hTF. The effect of the single R143A mutation on the kinetic profile of iron release provides a dramatic illustration of the dynamic nature of hTF.
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Affiliation(s)
- Shaina L Byrne
- Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, Vermont 05405, USA
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15
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Isolation and characterization of the iron-binding properties of a primitive monolobal transferrin from Ciona intestinalis. J Biol Inorg Chem 2008; 13:873-85. [DOI: 10.1007/s00775-008-0375-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Accepted: 04/04/2008] [Indexed: 11/25/2022]
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16
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On the evolutionary significance and metal-binding characteristics of a monolobal transferrin from Ciona intestinalis. Proc Natl Acad Sci U S A 2008; 105:3268-73. [PMID: 18287008 DOI: 10.1073/pnas.0705037105] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transferrins are a family of proteins that bind and transport Fe(III). Modern transferrins are typically bilobal and are believed to have evolved from an ancient gene duplication of a monolobal form. A novel monolobal transferrin, nicatransferrin (nicaTf), was identified in the primitive ascidian species Ciona intestinalis that possesses the characteristic features of the proposed ancestral Tf protein. In this work, nicaTf was expressed in Pichia pastoris. Extensive solution studies were performed on nicaTf, including UV-vis, fluorescence, CD, EPR and NMR spectroscopies, and electrospray time-of-flight mass spectrometry. The expressed protein is nonglycosylated, unlike the protein isolated from the organism. This property does not affect its ability to bind Fe(III). However, Fe(III)-bound nicaTf displays important spectral differences from other Fe(III)-bound transferrins, which are likely the consequence of differences in metal coordination. Coordination differences could also account for the weaker affinity of nicaTf for Fe(III) (log K = 18.5) compared with bilobal human serum transferrin (HsTf) (log K = 22.5 and 21.4). The Fe-nicaTf complex is not labile, as indicated by slow metal removal kinetics by the high-affinity chelator tiron at pH 7.4. The protein alternatively binds up to one equivalent of Ti(IV) or V(V), which suggests that it may transport nonferric metals. These solution studies provide insight into the structure and function of the primitive monolobal transferrin of C. intestinalis for comparison with higher order bilobal transferrins. They suggest that a major advantage for the evolution of modern transferrins, dominantly of bilobal form, is stronger Fe(III) affinity because of cooperativity.
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17
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LIU B, YANG BS. Synthesis and Kinetic Study on the Chromium(III) Complex [Cr(ASA)(en)2]Cl·2H2O. CHINESE J CHEM 2007. [DOI: 10.1002/cjoc.200790333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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18
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Liu B, Li YQ, Yang BS. Synthesis, characterization and kinetics properties of chromium(III) complex [Cr(3-HNA)(en)2]Cl·H2O·CH3OH. INORG CHEM COMMUN 2007. [DOI: 10.1016/j.inoche.2006.11.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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19
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Liu B, Li YQ, Yang BS, Huang SP. Synthesis, characterization and properties of chromium(III) complex [Cr(SA)(en)2]Cl·2H2O. J Inorg Biochem 2006; 100:1462-9. [PMID: 16764932 DOI: 10.1016/j.jinorgbio.2006.04.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Revised: 04/05/2006] [Accepted: 04/14/2006] [Indexed: 11/17/2022]
Abstract
The reaction of chromium(III) chloride, salicylic acid (SA) and ethylenediamine (en) led to the formation of chromium complex [Cr(SA)(en)(2)]Clx2H(2)O(1). The crystal structure belongs to monoclinic system with the space group P2(1), R(1)=0.0358. In this compound, Cr(III) atom is six-coordinated in octahedral coordination geometry by one phenolic hydroxyl oxygen, one carboxylate oxygen from the salicylic acid and four nitrogen atoms from two ethylenediamine molecules, respectively. The transfer manners of Cr(III) from the title compound to the low-molecular-mass chelator, ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) and the iron-binding protein apoovotransferrin (apoOTf) were followed by a combination of UV-visible (UV-Vis) and fluorescence spectra in 0.01M Hepes at pH 7.4. The results show that Cr(III) can be transferred from the complex to apoovotransferrin with the retention of the salicylate acted as a synergistic anion.
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Affiliation(s)
- Bin Liu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Molecular Science, Shanxi University, Taiyuan 030006, China
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Brook CE, Harris WR, Spilling CD, Peng W, Harburn JJ, Srisung S. Effect of Ligand Structure on the Pathways for Iron Release from Human Serum Transferrin. Inorg Chem 2005; 44:5183-91. [PMID: 15998048 DOI: 10.1021/ic050411m] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rate constants for the removal of iron from N-terminal monoferric transferrin have been measured for a series of phosphate and phosphonocarboxylic acids in pH 7.4 0.1 M hepes buffer at 25 degrees C. The bidentate ligands pyrophosphate and phosphonoacetic acid (PAA) show a combination of saturation and first-order kinetics with respect to the ligand concentration. Similar results are observed following a single substitution at the 2-position of PAA to give 2-benzyl-PAA and phosphonosuccinic acid. In contrast, disubstitution at the 2-position to form 2,2-dibenzyl-PAA leads to a marked reduction in iron removal via the first-order pathway. Rate constants were also measured for tripolyphosphate and phosphonodiacetic acid, which are elongated versions of PP(i) and PAA. In both cases, this elongation completely eliminates the first-order component for iron release while having relatively little impact on the saturation pathway. The sensitivity of the first-order component to the structure of the ligand strongly indicates that this pathway involves the binding of the ligand to a specific site on the protein and cannot be attributed to changes in the overall ionic strength of the solution as the ligand concentration increases. It is proposed that this structural sensitivity reflects steric restrictions on the ability of the incoming ligand to substitute for the synergistic carbonate anion to form a relatively unstable Fe-ligand-Tf ternary intermediate, which then dissociates to FeL and apoTf.
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Affiliation(s)
- Claire E Brook
- Department of Chemistry & Biochemistry, University of Missouri-St. Louis, St. Louis, Missouri 63121-4499, USA
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21
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Deligiannakis Y, Louloudi M, Hadjiliadis N. Electron spin echo envelope modulation (ESEEM) spectroscopy as a tool to investigate the coordination environment of metal centers. Coord Chem Rev 2000. [DOI: 10.1016/s0010-8545(99)00218-0] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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22
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Zhou Y, Bowler BE, Eaton GR, Eaton SS. Electron spin-lattice relaxation rates for high-spin Fe(III) complexes in glassy solvents at temperatures between 6 and 298 K. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2000; 144:115-122. [PMID: 10783280 DOI: 10.1006/jmre.2000.2047] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The temperature dependence of spin-lattice relaxation rates was analyzed for four high-spin nonheme iron proteins between 5 and 20 K, for three high-spin iron porphyrins between 5 and 118 K, and for four high-spin heme proteins between 5 and 150 to 298 K. For the nonheme proteins the zero-field splittings, D, are less than 0.7 cm(-1), and the relaxation is dominated by the Orbach and Raman processes. For the iron porphyrins and heme proteins D is between 4 and 12 cm(-1) and the relaxation is dominated by the Orbach process between about 5 and 100 K and by a local mode at higher temperatures. The relaxation rates for the heme proteins in glassy matrices extrapolated to values at room temperature that are similar to values obtained by NMR relaxivity in fluid solution. This similarity suggests that for high-spin Fe(III) heme proteins with effective intramolecular spin-lattice relaxation processes, the additional motional freedom gained when a relatively large protein goes from glassy solid to liquid solution at room temperature has little impact on spin-lattice relaxation.
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Affiliation(s)
- Y Zhou
- Department of Chemistry and Biochemistry, University of Denver, Colorado 80208, USA
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23
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Gaffney BJ, Silverstone HJ. Simulation methods for looping transitions. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1998; 134:57-66. [PMID: 9740731 DOI: 10.1006/jmre.1998.1526] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Looping transitions occur in field-swept electron magnetic resonance spectra near avoided crossings and involve a single pair of energy levels that are in resonance at two magnetic field strengths, before and after the avoided crossing. When the distance between the two resonances approaches a linewidth, the usual simulation of the spectra, which results from a linear approximation of the dependence of the transition frequency on magnetic field, breaks down. A cubic approximation to the transition frequency, which can be obtained from the two resonance fields and the field-derivatives of the transition frequencies, along with linear (or better) interpolation of the transition-probability factor, restores accurate simulation. The difference is crucial for accurate line shapes at fixed angles, as in an oriented single crystal, but the difference turns out to be a smaller change in relative intensity for a powder spectrum. Spin-3/2 Cr3+ in ruby and spin-5/2 Fe3+ in transferrin oxalate are treated as examples.
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Affiliation(s)
- B J Gaffney
- National High Magnetic Field Laboratory and Institute for Molecular Biophysics, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, Florida, 32310, USA
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24
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Gaffney BJ, Eaton GR, Eaton SS. Electron Spin Relaxation Rates for High-Spin Fe(III) in Iron Transferrin Carbonate and Iron Transferrin Oxalate. J Phys Chem B 1998; 102:5536-41. [PMID: 16429607 PMCID: PMC1317103 DOI: 10.1021/jp981595b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To optimize simulations of CW EPR spectra for high-spin Fe(III) with zero-field splitting comparable to the EPR quantum, information is needed on the factors that contribute to the line shapes and line widths. Continuous wave electron paramagnetic resonance (EPR) spectra obtained for iron transferrin carbonate from 4 to 150 K and for iron transferrin oxalate from 4 to 100 K did not exhibit significant temperature dependence of the line shape, which suggested that the line shapes were not relaxation determined. To obtain direct information concerning the electron spin relaxation rates, electron spin echo and inversion recovery EPR were used to measure T(1) and T(m) for the high-spin Fe(III) in iron transferrin carbonate and iron transferrin oxalate between 5 and 20-30 K. For comparison with the data for the transferrin complexes, relaxation times were obtained for tris(oxalato)ferrate(III). The relaxation rates are similar for the three complexes and do not exhibit a strong dependence on position in the spectrum. Extrapolation of the observed temperature dependence of the relaxation rates to higher temperatures gives values consistent with the conclusion that the CW line shapes are not relaxation determined up to 150 K.
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Affiliation(s)
- B J Gaffney
- National High Magnetic Field Laboratory & Department of Biological Science, Florida State University, Tallahassee, Florida 32310
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25
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Maguire BC, Gaffney BJ. Interdoublet transitions in S = 5/2 protein systems. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1997; 9:81-83. [PMID: 9413907 DOI: 10.1016/s0926-2040(97)00047-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Beginning with known parameters that characterize the EMR spectra of several proteins containing high-spin ferric iron, the information content of the spectra has been examined by simulations that cover a range of magnetic fields and frequencies. Transitions between levels that are not Kramers doublet levels are particularly interesting when the applied frequency is approximately two to three times the value of the zero-field splitting parameter, D. In these cases, transitions at very low magnetic fields correspond to portions of interdoublet transitions that are well separated from all other transitions. The magnetic field is aligned at angles between the molecular principal axes for the portion of the molecules giving rise to the low-field interdoublet transitions. This provides an opportunity for unique angle-selection experiments.
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Affiliation(s)
- B C Maguire
- National High Magnetic Field Laboratory, Florida State University, Tallahassee 32306, USA
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26
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Bailey CT, Byrne C, Chrispell K, Molkenbur C, Sackett M, Reid K, McCollum K, Vibbard D, Catelli R. Effect of a covalently attached synergistic anion on chelator-mediated iron-release from ovotransferrin: additional evidence for two concurrent pathways. Biochemistry 1997; 36:10105-8. [PMID: 9254606 DOI: 10.1021/bi961430y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mechanism by which the iron-transport protein transferrin releases its iron in vivo is presently unclear. In vitro studies have implicated two concurrent chelator-mediated iron-release pathways: one which is hyperbolic in nature, involving a conformational change in the protein as a rate limiting step, and a second which has been proposed to be first-order in nature and to involve initial release of a synergistic anion. We have examined the effect that an affinity-label analog of the synergistic anion has on chelator-mediated iron-release from this protein. A covalently attached anion would inhibit iron-release via any pathway in which anion release is a prerequisite to iron release. The present investigation examined the effect that the covalently attached anion had on iron-release to pyrophosphate (PPi) and N, N-bis(phosphonomethyl)glycine (DPG), two chelators which are believed to utilize both pathways concurrently. Results show that when the affinity-label anion is utilized, strictly hyperbolic data are obtained, with similar observed kmax values. This is strong support for the hypothesis of a common, chelator-independent rate-limiting step for the one available pathway. These results also support strongly the hypothesis that synergistic anion removal is a prerequisite step to iron-release via the second pathway.
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Affiliation(s)
- C T Bailey
- Department of Biological and Chemical Sciences, Wells College, Aurora, New York 13026, USA
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27
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Deligiannakis Y, Boussac A, Bottin H, Perrier V, Bârzu O, Gilles AM. A new non-heme iron environment in Paracoccus denitrificans adenylate kinase studied by electron paramagnetic resonance and electron spin echo envelope modulation spectroscopy. Biochemistry 1997; 36:9446-52. [PMID: 9235989 DOI: 10.1021/bi970021e] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Adenylate kinase from the Gram-negative bacterium Paracoccus denitrificans (AKden) has structural features highly similar to those of the enzyme from Gram-positive organisms. Atomic absorption spectroscopy of the recombinant protein, which is a dimer, revealed the presence of two metals, zinc and iron, each binding most probably to one monomer. Under oxidizing conditions, the electron paramagnetic resonance (EPR) spectrum of AKden at 4.2 K consists of features at g = 9.23, 4.34, 4.21, and 3.68. These features are absent in the ascorbate-reduced protein and are characteristic of a S = 5/2 spin system in a rhombic environment with E/D = 0.24 and are assigned to a non-heme Fe3+ (S = 5/2) center. The zero-field splitting parameter D (D = 1.4 +/- 0.2 cm-1) was estimated from the temperature dependence of the EPR spectra. These EPR characteristic as well as the difference absorption spectrum (oxidized minus reduced) of AKden are similar to those reported for the non-heme iron protein rubredoxin. Nevertheless, the redox potential of the Fe2+/Fe3+ couple in AKden was measured at +230 +/- 30 mV, which is more positive than the redox potential of the non-heme iron in rubredoxin. Binding of cyanide converts the iron from the high-spin (S = 5/2) to the low-spin (S = 1/2) spin state. The EPR spectrum of the non-heme Fe3+(S = 1/2) in the presence of cyanide has g values of 2.45, 2.18, and 1.92 and spin-Hamiltonian parameters R/lambda = 7. 4 and R/mu = 0.56. The conversion of the non-heme iron to the low-spin (S = 1/2) state allowed the study of its local environment by electron spin echo envelope modulation spectroscopy (ESEEM). The ESEEM data revealed the existence of 14N or 15N nuclei coupled to the low-spin iron after addition of KC14N or KC15N respectively. This demonstrated that iron in AKden has at least one labile coordination position that can be easily occupied by cyanide. Other possible magnetic interactions with nitrogen(s) from the protein are discussed.
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Affiliation(s)
- Y Deligiannakis
- Section de Bioénergétique, URA CNRS 2096, Département de Biologie Cellulaire et Moléculaire, CEA Saclay, 91191 Gif-sur-Yvette, France
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28
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Kinetics of iron removal from monoferric and cobalt-labelled monoferric transferrins by ethylenediaminetetra(methylenephosphonic acid) and ethylenediaminetetraacetic acid. Polyhedron 1997. [DOI: 10.1016/s0277-5387(96)00412-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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29
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Baker HM, Anderson BF, Brodie AM, Shongwe MS, Smith CA, Baker EN. Anion binding by transferrins: importance of second-shell effects revealed by the crystal structure of oxalate-substituted diferric lactoferrin. Biochemistry 1996; 35:9007-13. [PMID: 8703903 DOI: 10.1021/bi960288y] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Proteins of the transferrin family bind, with high affinity, two Fe3+ ions and two CO3(2)- ions but can also bind other metal ions and other anions. In order to find out how the protein structure and its two binding sites adapt to the binding of larger anions, we have determined the crystal structure of oxalate-substituted diferric lactoferrin at 2.4 A resolution. The final model has a crystallographic R-factor of 0.196 for all data in the range 8.0-2.4 A. Substitution of oxalate for carbonate does not produce any significant change in the polypeptide folding or domain closure. Both binding sites are perturbed, however, and the effects are different in each. In the C-lobe site the oxalate ion is bound to iron in symmetric 1,2-bidentate fashion whereas in the N-lobe the anion coordination is markedly asymmetric. The difference arises because in each site substitution of the larger anion causes displacement of the arginine that forms one wall of the anion binding site; the movement is different in each case, however, because of different interactions with "second shell" amino acid residues in the binding cleft. These observations provide an explanation for the site inequivalences that accompany the substitution of non-native anions and cations.
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Affiliation(s)
- H M Baker
- Department of Chemistry and Biochemistry, Massey University, Palmerston North, New Zealand.
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30
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Aramini JM, Saponja JA, Vogel HJ. Spectroscopic studies of the interaction of aluminum(III) with transferrins. Coord Chem Rev 1996. [DOI: 10.1016/s0010-8545(96)90026-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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31
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Grady JK, Mason AB, Woodworth RC, Chasteen ND. The effect of salt and site-directed mutations on the iron(III)-binding site of human serum transferrin as probed by EPR spectroscopy. Biochem J 1995; 309 ( Pt 2):403-10. [PMID: 7626003 PMCID: PMC1135746 DOI: 10.1042/bj3090403] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effects of site-directed mutation and salt on the iron(III)-binding site of the recombinant half-molecule of the N-terminal lobe (hTf/2N) of human transferrin was studied by EPR spectroscopy. Changes were observed in the EPR spectra of all variants investigated (D63S, D63C, G65R, K206Q, H207E, H249E, H249Q, K296E and K296Q) compared with that of the wild-type protein. The most pronounced changes in the metal site were caused by replacement of the coordinating residues, Asp-63 and His-249, and the non-coordinating residue Lys-296, which is located in the hinge region of the iron-binding cleft. The EPR spectral changes from replacement of other non-coordinating residues were more subtle, indicating small changes in Fe3+ coordination to the protein. The EPR spectrum of variant G65R suggests that it adopts two distinct conformations in solution, one in which the two domains forming the iron-binding cleft are closed and one in which they are open; in the latter instance Asp-63 is no longer coordinated to the Fe3+. Chloride-binding studies on hTf/2N, K206Q, H207E, K296Q and K296E showed similar binding isotherms, indicating that none of the hinge region residues replaced, i.e. Lys-206, His-207 or Lys-296, are the sites of chloride binding. The results show that the coordination environment of the Fe3+ is sensitive to structural changes from site-directed mutation of both remote and coordinated residues and also to chloride-binding and ionic strength effects.
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Affiliation(s)
- J K Grady
- Department of Chemistry, Parsons Hall, University of New Hampshire, Durham 03824-3598, USA
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32
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Ross DC, Egan TJ, Purves LR. Periodate modification of human serum transferrin Fe(III)-binding sites. Inhibition of carbonate insertion into Fe(III)- and Cu(II)-chelator-transferrin ternary complexes. J Biol Chem 1995; 270:12404-10. [PMID: 7759481 DOI: 10.1074/jbc.270.21.12404] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Periodate modification of human serum transferrin produces a species that binds Fe(III) weakly at pH 7.4 contrary to previous reports that Fe(III)-binding activity is completely lost. Ternary complexes of periodate-modified transferrin and either Fe(III) with nitrilotriacetate (NTA), oxalate, citrate, or EDTA, or of Cu(II) with oxalate could be formed. Peak wavelength maxima of these spectral bands are identical to those reported for native transferrin in the absence of bicarbonate. No carbonate ternary complexes of periodate-modified transferrin with Fe(III), Al(III), Cu(II), or Zn(II) could be formed. Conditional (Fe(NTA)) binding constants (log K) for C- and N-terminal modified sites are 7.33 and 7.54, respectively. The respective extinction coefficients at 470 nm are decreased 45% compared with the native protein. The electron paramagnetic resonance spectrum of the complex closely resembles that of the Fe(III)-NTA ternary complex formed with native transferrin in the absence of bicarbonate. Anions, including bicarbonate, at high concentrations destabilize formation of this Fe(III)-NTA ternary complex, while Fe(III) chelators readily remove the bound Fe(III). Bicarbonate, sulfate, and pyrophosphate still bind to the modified binding sites in the absence of metal although with slightly lower affinity and with lower molar difference absorptivities. Results are interpreted as an inhibition of a crucial protein conformational change by an intramolecular cross-link, preventing formation of the particularly stable metal-carbonate ternary complex from the less stable metal-chelate ternary complex. The method can be used to produce monosited transferrins.
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Affiliation(s)
- D C Ross
- Department of Chemical Pathology, University of Cape Town, Red Cross War Memorial Children's Hospital, Rondebosch, South Africa
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33
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Binding of carboxylate anions at the non-heme Fe(II) of PS II. I. Effects on the Q−AFe2+ and QAFe3+ EPR spectra and the redox properties of the iron. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1994. [DOI: 10.1016/0005-2728(94)90044-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Petrouleas V, Deligiannakis Y, Diner B. Binding of carboxylate anions at the non-heme Fe(II) of PS II. II. Competition with bicarbonate and effects on the QAQB electron transfer rate. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1994. [DOI: 10.1016/0005-2728(94)90045-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Smith CA, Baker HM, Shongwe MS, Anderson BF, Baker EN. Crystallographic studies on metal and anion substituted human lactoferrin. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1994; 357:265-9. [PMID: 7762442 DOI: 10.1007/978-1-4615-2548-6_29] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- C A Smith
- Department of Chemistry and Biochemistry, Massey University, Palmerston North, New Zealand
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Brodie AM, Ainscough EW, Baker EN, Baker HM, Shongwe MS, Smith CA. Synergism and substitution in the lactoferrins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1994; 357:33-44. [PMID: 7762444 DOI: 10.1007/978-1-4615-2548-6_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The anion binding properties of human lactoferrin (Lf), with Fe3+ or Cu2+ as the associated metal ion, highlight differences between the two sites, and in the anion binding behaviour when different metals are bound. Carbonate, oxalate and hybrid carbonate-oxalate complexes have been prepared and their characteristic electronic and EPR spectra recorded. Oxalate can displace carbonate from either one or both anion sites of Cu2(CO3)2Lf, depending on the oxalate concentration, but no such displacement occurs for Fe2(CO3)2Lf although it does for the bovine analogue. Addition of oxalate and the appropriate metal ion to apoLf under carbonate-free conditions gives dioxalate complexes with both Fe3+ and Cu2+. The anion sites as determined from the crystal structures of Fe2(CO3)2Lf, Fe2(C2O4)2Lf, Cu2(CO3)2Lf, and Cu2(CO3)(C2O4)Lf have been compared. Both the carbonate and oxalate ions bind in bidentate fashion to the metal, except that the carbonate ion in the N-lobe site of dicupric lactoferrin is monodentate. The hybrid copper lactoferrin complex shows that the oxalate ion binds preferentially in the C-lobe site in a bidentate mode. A series of complexes containing the synergistic anion O,N-chelates with increasing substitution on the N atom (glycinate, iminodiacetate and nitrilotriacetate) have been prepared with iron bovine lactoferrin for comparison with the O,O-chelate oxalate. Overall these observations lead to a generalised model for synergistic anion binding by transferrins and allow comparisons to be made with nonsynergistic anions such as citrate and succinate.
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Affiliation(s)
- A M Brodie
- Department of Chemistry and Biochemistry, Massey University, Palmerston North, New Zealand
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38
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Gaffney BJ, Silverstone HJ. Simulation of the EMR Spectra of High-Spin Iron in Proteins. EMR OF PARAMAGNETIC MOLECULES 1993. [DOI: 10.1007/978-1-4615-2892-0_1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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39
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Woodworth RC, Mason AB, Funk WD, MacGillivray RT. Expression and initial characterization of five site-directed mutants of the N-terminal half-molecule of human transferrin. Biochemistry 1991; 30:10824-9. [PMID: 1932003 DOI: 10.1021/bi00109a002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Five site-directed mutants of the N-terminal half-molecule of human serum transferrin have been expressed in baby hamster kidney cells and purified to homogeneity. Expression levels and overall yields varied considerably from the wild-type protein, depending on the mutant in question. The mutants are D63S, D63C, G65R, K206Q, and H207E and are based on mutations observed in a variety of transferrins of known sequence. Their molecular masses, determined by electrospray mass spectrometry, agree with theory, except for the D63C mutant, which appears to be cysteinylated. All mutants bind iron but with varying affinities; qualitatively, in increasing order D63S approximately D63C approximately G65R much less than wild type less than or equal to H207E much less than K206Q. In general, reduction of formal negative charge within the binding cleft shifts the visible spectral maximum of the iron complex toward the blue and reduces the affinity for iron, and increasing the formal negative charge shifts the visible maximum toward the red and increases the affinity for iron. The K206Q mutant is exceptional inasmuch as its visible maximum shows a blue shift, but its affinity for iron is the greatest of all of the mutants studied. All mutants reported, in addition to the wild-type protein, exhibit very similar visible molar extinction coefficients for the iron complex and very similar changes in extinction coefficients at 240 nm on binding Fe(III) or Ga(III). These results suggest that in all cases the bound metal ion is coordinated by two tyrosyl side chains.
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Affiliation(s)
- R C Woodworth
- Department of Biochemistry, University of Vermont College of Medicine, Burlington 05482-0068
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