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MacGillivray RTA, Conway EM. Obituary for Earl Warren Davie 1927‐2020. J Thromb Haemost 2020. [DOI: 10.1111/jth.14978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ross T. A. MacGillivray
- Faculty of Medicine Centre for Blood Research Life Sciences Institute University of British Columbia Vancouver BC Canada
| | - Edward M. Conway
- Faculty of Medicine Centre for Blood Research Life Sciences Institute University of British Columbia Vancouver BC Canada
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Falkner FG, Turecek PL, MacGillivray RTA, Bodemer W, Scheiflinger F, Kandels S, Mitterer A, Kistner O, Barrett N, Eibl J, Dorner F. High Level Expression of Active Human Prothrombin in a Vaccina Virus Expression System. Thromb Haemost 2018. [DOI: 10.1055/s-0038-1656335] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
SummaryWe have worked out an efficient and time saving procedure for the expression of recombinant human prothrombin. The glycoprotein was expressed in the vaccinia virus expression system in several mammalian cell lines. The kidney cell lines Vero and BHK and the human cell line Hela were found to efficiently secrete prothrombin. Expression levels of 3–4 µg of factor II per 106 cells per day corresponding to 18–23 mU per 106 cells per day were achieved. Since the expression levels obtained with the vaccinia virus/Vero cell system were comparable to those obtained in amplified transformed CHO cells it provides an alternative system for the efficient expression of human prothrombin and may allow to further elucidate structure-function relationships of (pro)thrombin and its various effectors.
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Affiliation(s)
- F G Falkner
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - P L Turecek
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - R T A MacGillivray
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - W Bodemer
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - F Scheiflinger
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - S Kandels
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - A Mitterer
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - O Kistner
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - N Barrett
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - J Eibl
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
| | - F Dorner
- The Immuno AG, Biomedical Research Center, Orth/Donau, Austria, and the University of British Columbia, Department of Biochemistry, Vancouver, B. C., Canada
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3
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Adam N, Trumm M, Smith VC, MacGillivray RTA, Panak PJ. Incorporation of transuranium elements: coordination of Cm(iii) to human serum transferrin. Dalton Trans 2018; 47:14612-14620. [DOI: 10.1039/c8dt02915f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Structure determination of Cm(iii)-transferrin by a combined spectroscopic and theoretical approach gives insight into the biochemical behaviour of incorporated actinides.
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Affiliation(s)
- Nicole Adam
- Karlsruhe Institute of Technology (KIT)
- Campus North
- Institute for Nuclear Waste Disposal (INE)
- 76021 Karlsruhe
- Germany
| | - Michael Trumm
- Karlsruhe Institute of Technology (KIT)
- Campus North
- Institute for Nuclear Waste Disposal (INE)
- 76021 Karlsruhe
- Germany
| | - Val C. Smith
- University of British Columbia
- Department of Biochemistry and Molecular Biology and Centre for Blood Research
- Vancouver
- Canada
| | - Ross T. A. MacGillivray
- University of British Columbia
- Department of Biochemistry and Molecular Biology and Centre for Blood Research
- Vancouver
- Canada
| | - Petra J. Panak
- Karlsruhe Institute of Technology (KIT)
- Campus North
- Institute for Nuclear Waste Disposal (INE)
- 76021 Karlsruhe
- Germany
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Vanden Hoek AL, Talbot K, Carter ISR, Vickars L, Carter CJ, Jackson SC, MacGillivray RTA, Pryzdial ELG. Coagulation factor X Arg386 specifically affects activation by the intrinsic pathway: a novel patient mutation. J Thromb Haemost 2012; 10:2613-5. [PMID: 23039000 DOI: 10.1111/jth.12021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Curtis SB, Dunbar WS, MacGillivray RTA. Bacteriophage-induced aggregation of oil sands tailings. Biotechnol Bioeng 2012; 110:803-11. [PMID: 23055243 DOI: 10.1002/bit.24745] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 09/12/2012] [Accepted: 09/24/2012] [Indexed: 11/08/2022]
Abstract
Very large quantities of tailings are produced as a result of processing oil sands. After the sand particles settle out, a dense stable mixture of clay, silt, water with residual bitumen, salts, and organics called mature fine tailings (MFT) can remain in suspension for decades. Research into developing methods that would allow consolidation and sedimentation of the suspended particles is ongoing. We have studied the ability of a filamentous bacteriophage (called VP12 bearing the peptide DSQKTNPS at the N-terminus of the major coat protein pVIII) to aggregate MFT. To understand the biophysical basis of the aggregation, phage-induced aggregation of diluted MFT was measured at room temperature under varying conditions of pH, salt, detergent. Phage at concentrations of 5.0 × 10(11)/mL to 10(12)/mL induced rapid settling of the diluted MFT. The addition of sodium chloride (10 mM) lowered the concentration of phage required to induce aggregation. Since the non-ionic detergents Triton-X 100 and Tween-20, and the ionic detergent sodium deoxycholate had little effect, hydrophobic interactions do not appear to be a major contributor to the phage-induced aggregation of MFT. However, aggregation was prevented at pH values higher than 9.0 suggesting that positively charged amino acid residues are required for MFT aggregation by phage. Genetic engineering of the pVIII peptide sequence indicated that hydrogen bonding also contributes to phage-induced aggregation. In addition, replacing the basic residue lysine with an alanine in the recombinant peptide of VP12 completely prevented phage-induced aggregation. Three other phage displaying different amino acid sequences but all containing a lysine in the same position had variable aggregation efficiencies, ranging from no aggregation to rapid aggregation. We conclude that not only are the functional groups of the amino acids important, but the conformation that is adopted by the variable pVIII peptide is also important for phage-induced MFT aggregation.
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Affiliation(s)
- Susan B Curtis
- Norman B. Keevil Institute of Mining Engineering, University of British Columbia, Vancouver, British Columbia, Canada.
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Grieco SHH, Wong AYK, Dunbar WS, MacGillivray RTA, Curtis SB. Optimization of fermentation parameters in phage production using response surface methodology. J Ind Microbiol Biotechnol 2012; 39:1515-22. [PMID: 22714954 DOI: 10.1007/s10295-012-1148-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 05/04/2012] [Indexed: 10/28/2022]
Abstract
Previously, we used computer-controlled fermentation technology to improve the yield of filamentous phage produced in Escherichia coli by 10-fold (Grieco et al., Bioprocess Biosyst Eng 32:773-779, 2009). In the current study, three major fermentation parameters (temperature, dissolved oxygen [DO], and pH) were investigated using design of experiments (DOE) methodology. Response surface methodology (RSM) was employed to create a process model and determine the optimal conditions for maximal phage production. The experimental data fitted best to a quadratic model (p < 0.0001). Temperature and pH, but not DO, proved to be significant variables. The model predicted a theoretical optimal condition for maximal bacteriophage production at temperature of 28.1 °C and pH 6.9. A validation run resulted in phage production [3.49 × 10(11) transducing units (TU)/mL] comparable to the predicted value (2.86 × 10(11) TU/mL). This represented a 7-fold increase in phage production above that obtained without optimization, resulting in a 70-fold increase above that achieved by shake flask culture alone.
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Affiliation(s)
- Sung-Hye H Grieco
- Centre for Blood Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
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Steere AN, Chasteen ND, Miller BF, Smith VC, MacGillivray RTA, Mason AB. Structure-based mutagenesis reveals critical residues in the transferrin receptor participating in the mechanism of pH-induced release of iron from human serum transferrin. Biochemistry 2012; 51:2113-21. [PMID: 22356162 DOI: 10.1021/bi3001038] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The recent crystal structure of two monoferric human serum transferrin (Fe(N)hTF) molecules bound to the soluble portion of the homodimeric transferrin receptor (sTFR) has provided new details about this binding interaction that dictates the delivery of iron to cells. Specifically, substantial rearrangements in the homodimer interface of the sTFR occur as a result of the binding of the two Fe(N)hTF molecules. Mutagenesis of selected residues in the sTFR highlighted in the structure was undertaken to evaluate the effect on function. Elimination of Ca(2+) binding in the sTFR by mutating two of four coordinating residues ([E465A,E468A]) results in low production of an unstable and aggregated sTFR. Mutagenesis of two histidines ([H475A,H684A]) at the dimer interface had little effect on the kinetics of release of iron at pH 5.6 from either lobe, reflecting the inaccessibility of this cluster to solvent. Creation of an H318A sTFR mutant allows assignment of a small pH-dependent initial decrease in the magnitude of the fluorescence signal to His318. Removal of the four C-terminal residues of the sTFR, Asp757-Asn758-Glu759-Phe760, eliminates pH-stimulated release of iron from the C-lobe of the Fe(2)hTF/sTFR Δ757-760 complex. The inability of this sTFR mutant to bind and stabilize protonated hTF His349 (a pH-inducible switch) in the C-lobe of hTF accounts for the loss. Collectively, these studies support a model in which a series of pH-induced events involving both TFR residue His318 and hTF residue His349 occurs to promote receptor-stimulated release of iron from the C-lobe of hTF.
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Affiliation(s)
- Ashley N Steere
- Department of Biochemistry, University of Vermont, College of Medicine, Burlington, Vermont 05405, United States
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Steere AN, Miller BF, Roberts SE, Byrne SL, Chasteen ND, Smith VC, MacGillivray RTA, Mason AB. Ionic residues of human serum transferrin affect binding to the transferrin receptor and iron release. Biochemistry 2012; 51:686-94. [PMID: 22191507 DOI: 10.1021/bi201661g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Efficient delivery of iron is critically dependent on the binding of diferric human serum transferrin (hTF) to its specific receptor (TFR) on the surface of actively dividing cells. Internalization of the complex into an endosome precedes iron removal. The return of hTF to the blood to continue the iron delivery cycle relies on the maintenance of the interaction between apohTF and the TFR after exposure to endosomal pH (≤6.0). Identification of the specific residues accounting for the pH-sensitive nanomolar affinity with which hTF binds to TFR throughout the cycle is important to fully understand the iron delivery process. Alanine substitution of 11 charged hTF residues identified by available structures and modeling studies allowed evaluation of the role of each in (1) binding of hTF to the TFR and (2) TFR-mediated iron release. Six hTF mutants (R50A, R352A, D356A, E357A, E367A, and K511A) competed poorly with biotinylated diferric hTF for binding to TFR. In particular, we show that Asp356 in the C-lobe of hTF is essential to the formation of a stable hTF-TFR complex: mutation of Asp356 in the monoferric C-lobe hTF background prevented the formation of the stoichiometric 2:2 (hTF:TFR monomer) complex. Moreover, mutation of three residues (Asp356, Glu367, and Lys511), whether in the diferric or monoferric C-lobe hTF, significantly affected iron release when in complex with the TFR. Thus, mutagenesis of charged hTF residues has allowed identification of a number of residues that are critical to formation of and release of iron from the hTF-TFR complex.
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Affiliation(s)
- Ashley N Steere
- Department of Biochemistry, University of Vermont, College of Medicine, Burlington, Vermont 05405, United States
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Vashchenko G, Bleackley MR, Griffiths TAM, MacGillivray RTA. Oxidation of organic and biogenic amines by recombinant human hephaestin expressed in Pichia pastoris. Arch Biochem Biophys 2011; 514:50-6. [PMID: 21802403 DOI: 10.1016/j.abb.2011.07.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 06/28/2011] [Accepted: 07/12/2011] [Indexed: 11/15/2022]
Abstract
Hephaestin is a multicopper ferroxidase involved in iron absorption in the small intestine. Expressed mainly on the basolateral surface of duodenal enterocytes, hephaestin facilitates the export of iron from the intestinal epithelium into blood by oxidizing Fe(2+) into Fe(3+), the only form of iron bound by the plasma protein transferrin. Structurally, the human hephaestin ectodomain is predicted to resemble ceruloplasmin, the major multicopper oxidase in blood. In addition to its ferroxidase activity, ceruloplasmin was reported to oxidize a wide range of organic compounds including a group of physiologically relevant substrates (biogenic amines). To study oxidation of organic substrates, the human hephaestin ectodomain was expressed in Pichia pastoris. The purified recombinant hephaestin has an average copper content of 4.2 copper atoms per molecule. The K(m) for Fe(2+) of hephaestin was determined to be 3.2μM which is consistent with the K(m) values for other multicopper ferroxidases. In addition, the K(m) values of hephaestin for such organic substrates as p-phenylenediamine and o-dianisidine are close to values determined for ceruloplasmin. However, in contrast to ceruloplasmin, hephaestin was incapable of direct oxidation of adrenaline and dopamine implying a difference in biological substrate specificities between these two homologous ferroxidases.
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Affiliation(s)
- Ganna Vashchenko
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada
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10
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Curtis SB, MacGillivray RTA, Dunbar WS. Effects of bacteriophage on the surface properties of chalcopyrite (CuFeS₂), and phage-induced flocculation of chalcopyrite, glacial till, and oil sands tailings. Biotechnol Bioeng 2011; 108:1579-90. [PMID: 21337331 DOI: 10.1002/bit.23097] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 01/27/2011] [Accepted: 02/04/2011] [Indexed: 11/08/2022]
Abstract
The binding of mineral-specific phage to the surface of chalcopyrite (CuFeS(2)) was investigated by using X-ray photoelectron spectroscopy and scanning Auger microscopy. These studies confirmed the elemental composition of the minerals and confirmed that bacteriophage were bound to the mineral surface. These techniques also revealed that the phage were not forming a continuous film over the entire surface of the CuFeS(2) particles, but selectively bound to the slimes coating the particles. In addition, the effect of mineral-specific phage binding to the surface of CuFeS(2) was investigated using induction time and zeta potential measurements. Bacteriophage (10(12) /mL) increased the induction time (contact time resulting in 50% particle attachment to a bubble) from ∼7.5 to ∼17 ms and reversed the zeta potential from negative to positive. In the course of performing the zeta potential measurements on particles <45 µm in diameter, phage-induced aggregation was observed. The mechanism of aggregation was explored using a range of pH (3-11) and cation concentrations. Aggregation was observed across the tested pH range and with all cations. Phage also mediated aggregation of glacial till and oil sands tailings in a dose-dependent and particle size-dependent manner. We conclude that binding of bacteriophage to the surface of CuFeS(2) does alter its surface properties.
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Affiliation(s)
- Susan B Curtis
- Norman B. Keevil Institute of Mining Engineering, 517-6350 Stores Road, Vancouver, BC, Canada V6T1Z4
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11
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Bleackley MR, Young BP, Loewen CJR, MacGillivray RTA. High density array screening to identify the genetic requirements for transition metal tolerance in Saccharomyces cerevisiae. Metallomics 2011; 3:195-205. [PMID: 21212869 DOI: 10.1039/c0mt00035c] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Biological systems have developed with a strong dependence on transition metals for accomplishing a number of biochemical reactions. Iron, copper, manganese and zinc are essential for virtually all forms of life with their unique chemistries contributing to a variety of physiological processes including oxygen transport, generation of cellular energy and protein structure and function. Properties of these metals (and to a lesser extent nickel and cobalt) that make them so essential to life also make them extremely cytotoxic in many cases through the formation of damaging oxygen radicals via Fenton chemistry. While life has evolved to exploit the chemistries of transition metals to drive physiological reactions, systems have concomitantly evolved to protect against the damaging effects of these same metals. Saccharomyces cerevisiae is a valuable tool for studying metal homeostasis with many of the genes identified thus far having homologs in higher eukaryotes including humans. Using high density arrays, we have screened a haploid S. cerevisiae deletion set containing 4786 non-essential gene deletions for strains sensitive to each of Fe, Cu, Mn, Ni, Zn and Co and then integrated the six screens using cluster analysis to identify pathways that are unique to individual metals and others with function shared between metals. Genes with no previous implication in metal homeostasis were found to contribute to sensitivity to each metal. Significant overlap was observed between the strains that were sensitive to Mn, Ni, Zn and Co with many of these strains lacking genes for the high affinity Fe transport pathway and genes involved in vacuolar transport and acidification. The results from six genome-wide metal tolerance screens show that there is some commonality between the cellular defenses against the toxicity of Mn, Ni, Zn and Co with Fe and Cu requiring different systems. Additionally, potential new factors been identified that function in tolerance to each of the six metals.
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Affiliation(s)
- Mark R Bleackley
- Centre for Blood Research, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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12
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Talbot K, Song J, Hewitt J, Serrano K, Ho M, Carter CJ, MacGillivray RTA, Pryzdial ELG. A novel compensating mechanism for homozygous coagulation factor V deficiency suggested by enhanced activated partial thromboplastin time after reconstitution with normal factor V. Br J Haematol 2010; 151:198-200. [PMID: 20735394 DOI: 10.1111/j.1365-2141.2010.08336.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Steere AN, Byrne SL, Chasteen ND, Smith VC, MacGillivray RTA, Mason AB. Evidence that His349 acts as a pH-inducible switch to accelerate receptor-mediated iron release from the C-lobe of human transferrin. J Biol Inorg Chem 2010; 15:1341-52. [PMID: 20711621 PMCID: PMC4505821 DOI: 10.1007/s00775-010-0694-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 08/02/2010] [Indexed: 11/25/2022]
Abstract
His349 in human transferrin (hTF) is a residue critical to transferrin receptor (TFR)-stimulated iron release from the C-lobe. To evaluate the importance of His349 on the TFR interaction, it was replaced by alanine, aspartate, lysine, leucine, tryptophan, and tyrosine in a monoferric C-lobe hTF construct (Fe(C)hTF). Using a stopped-flow spectrofluorimeter, we determined rate processes assigned to iron release and conformational events (in the presence and in the absence of the TFR). Significantly, all mutant/TFR complexes feature dampened iron release rates. The critical contribution of His349 is most convincingly revealed by analysis of the kinetics as a function of pH (5.6-6.2). The Fe(C)hTF/TFR complex titrates with a pK(a) of approximately 5.9. By contrast, the H349A mutant/TFR complex releases iron at higher pH with a profile that is almost the inverse of that of the control complex. At the putative endosomal pH of 5.6 (in the presence of salt and chelator), iron is released from the H349W mutant/TFR and H349Y mutant/TFR complexes with a single rate constant similar to the iron release rate constant for the control; this suggests that these substitutions bypass the required pH-induced conformational change allowing the C-lobe to directly interact with the TFR to release iron. The H349K mutant proves that although the positive charge is crucial to complete iron release, the geometry at this position is also critical. The H349D mutant shows that a negative charge precludes complete iron release at pH 5.6 both in the presence and in the absence of the TFR. Thus, histidine uniquely drives the pH-induced conformational change in the C-lobe required for TFR interaction, which in turn promotes iron release.
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Affiliation(s)
- Ashley N. Steere
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA
| | - Shaina L. Byrne
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA
| | - N. Dennis Chasteen
- Department of Chemistry, Parsons Hall, University of New Hampshire, Durham, NH 03824, USA
| | - Valerie C. Smith
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Ross T. A. MacGillivray
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Anne B. Mason
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA
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Hudson DM, Curtis SB, Smith VC, Griffiths TAM, Wong AYK, Scudamore CH, Buchan AMJ, MacGillivray RTA. Human hephaestin expression is not limited to enterocytes of the gastrointestinal tract but is also found in the antrum, the enteric nervous system, and pancreatic {beta}-cells. Am J Physiol Gastrointest Liver Physiol 2010; 298:G425-32. [PMID: 20019163 DOI: 10.1152/ajpgi.00453.2009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hephaestin (Hp) is a membrane protein with ferroxidase activity that converts Fe(II) to Fe(III) during the absorption of nutritional iron in the gut. Using anti-peptide antibodies to predicted immunogenic regions of rodent Hp, previous immunocytochemical studies in rat, mouse, and human gut tissues localized Hp to the basolateral membranes of the duodenal enterocytes where the Hp was predicted to aid in the transfer of Fe(III) to transferrin in the blood. We used a recombinant soluble form of human Hp to obtain a high-titer polyclonal antibody to Hp. This antibody was used to identify the intracellular location of Hp in human gut tissue. Our immunocytochemical studies confirmed the previous localization of Hp in human enterocytes. However, we also localized Hp to the entire length of the gastrointestinal tract, the antral portion of the stomach, and to the enteric nervous system (both the myenteric and submucous plexi). Hp was also localized to human pancreatic beta-cells. In addition to its expression in the same cells as Hp, ferroportin was also localized to the ductal cells of the exocrine pancreas. The localization of the ferroxidase Hp to the neuronal plexi and the pancreatic beta cells suggests a role for the enzymatic function of Hp in the protection of these specialized cell types from oxidative damage.
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Affiliation(s)
- David M Hudson
- Centre for Blood Research and Department of Biochemistry, University of British Columbia, Vancouver, Canada
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15
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James NG, Byrne SL, Steere AN, Smith VC, MacGillivray RTA, Mason AB. Inequivalent contribution of the five tryptophan residues in the C-lobe of human serum transferrin to the fluorescence increase when iron is released. Biochemistry 2009; 48:2858-67. [PMID: 19281173 DOI: 10.1021/bi8022834] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human serum transferrin (hTF), with two Fe3+ binding lobes, transports iron into cells. Diferric hTF preferentially binds to a specific receptor (TFR) on the surface of cells, and the complex undergoes clathrin dependent receptor-mediated endocytosis. The clathrin-coated vesicle fuses with an endosome where the pH is lowered, facilitating iron release from hTF. On a biologically relevant time scale (2-3 min), the factors critical to iron release include pH, anions, a chelator, and the interaction of hTF with the TFR. Previous work, in which the increase in the intrinsic fluorescence signal was used to monitor iron release from the hTF/TFR complex, established that the TFR significantly enhances the rate of iron release from the C-lobe of hTF. In the current study, the role of the five C-lobe Trp residues in reporting the fluorescence change has been evaluated (+/-sTFR). Only four of the five recombinant Trp --> Phe mutants produced well. A single slow rate constant for iron release is found for the monoferric C-lobe (FeC hTF) and the four Trp mutants in the FeC hTF background. The three Trp residues equivalent to those in the N-lobe differed from the N-lobe and each other in their contributions to the fluorescent signal. Two rate constants are observed for the FeC hTF control and the four Trp mutants in complex with the TFR: k(obsC1) reports conformational changes in the C-lobe initiated by the TFR, and k(obsC2) is ascribed to iron release. Excitation at 295 nm (Trp only) and at 280 nm (Trp and Tyr) reveals interesting and significant differences in the rate constants for the complex.
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Affiliation(s)
- Nicholas G James
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington 05405, Vermont, USA
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16
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Mason AB, Byrne SL, Everse SJ, Roberts SE, Chasteen ND, Smith VC, MacGillivray RTA, Kandemir B, Bou-Abdallah F. A loop in the N-lobe of human serum transferrin is critical for binding to the transferrin receptor as revealed by mutagenesis, isothermal titration calorimetry, and epitope mapping. J Mol Recognit 2009; 22:521-9. [PMID: 19693784 PMCID: PMC4479294 DOI: 10.1002/jmr.979] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Transferrin (TF) is a bilobal transport protein that acquires ferric iron from the diet and holds it tightly within the cleft of each lobe (thereby preventing its hydrolysis). The iron is delivered to actively dividing cells by receptor mediated endocytosis in which diferric TF preferentially binds to TF receptors (TFRs) on the cell surface and the entire complex is taken into an acidic endosome. A combination of lower pH, a chelator, inorganic anions, and the TFR leads to the efficient release of iron from each lobe. Identification of residues/regions within both TF and TFR required for high affinity binding has been an ongoing goal in the field. In the current study, we created human TF (hTF) mutants to identify a region critical to the interaction with the TFR which also constitutes part of an overlapping epitope for two monoclonal antibodies (mAbs) to the N-lobe, one of which was previously shown to block binding of hTF to the TFR. Four single point mutants, P142A, R143A, K144A, and P145A in the N-lobe, were placed into diferric hTF. Isothermal titration calorimetry (ITC) revealed that three of the four residues (Pro142, Lys144, and Pro145) in this loop are essential to TFR binding. Additionally, Lys144 is common to the recognition of both mAbs which show different sensitivities to the three other residues. Taken together these studies prove that this loop is required for binding of the N-lobe of hTF to the TFR, provide a more precise description of the role of each residue in the loop in the interaction with the TFR, and confirm that the N-lobe is essential to high affinity binding of diferric hTF to TFR.
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Affiliation(s)
- Anne B Mason
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405, USA.
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17
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Au NHC, Wong AYK, Vickars L, MacGillivray RTA, Wadsworth LD. Two new examples of Hb St. Etienne [beta 92(F8)HisGln] in association with venous thrombosis. Hemoglobin 2009; 33:95-100. [PMID: 19373584 DOI: 10.1080/03630260902817206] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Hb St. Etienne [beta92(F8)HisGln] (also known as Hb Istanbul) is a rare unstable beta-globin chain variant that has been described in only three reports involving four patients. We report two individuals in a family of Scottish extraction whose members had been erroneously diagnosed to have hereditary spherocytosis (HS) and have now been shown to be heterozygotes for Hb St. Etienne. They also had venous thrombotic events with minimal provocation. This family illustrates the difficulties in identifying the cause of chronic hemolytic anemia and highlights the possible contribution of chronic hemolysis to increased risk of thrombosis.
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Affiliation(s)
- Nicholas H C Au
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada
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18
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James NG, Berger CL, Byrne SL, Smith VC, MacGillivray RTA, Mason AB. Intrinsic Fluorescence Reports a Global Conformational Change in the N-Lobe of Human Serum Transferrin following Iron Release†. Biochemistry 2007; 46:10603-11. [PMID: 17711300 DOI: 10.1021/bi602425c] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transferrins have been extensively studied in order to understand how they reversibly bind and release iron. Human serum transferrin (hTF) is a single polypeptide chain that folds into two lobes (N- and C-lobe); each lobe binds a single ferric ion. Iron release induces a large conformational change in each lobe. At the putative endosomal pH of 5.6, measurement of the increase in intrinsic fluorescence upon iron release from the recombinant N-lobe yields two rate constants: 8.9 min-1 and 1.3 min-1. Direct monitoring of iron release from the N-lobe at pH 5.6 (by the decrease in absorbance at 470 nm) gives a single rate constant of 9.1 min-1, definitively establishing that the faster rate constant in the fluorescent studies is due to iron release. To further elucidate the molecular basis of the intrinsic fluorescence change (and the source of the slower rate constant), we examined the contributions of the three individual tryptophan residues in the N-lobe (Trp8, Trp128, and Trp264). Three double mutants, each containing the single remaining tryptophan residue, were produced. In the iron-bound N-lobe, Trp128 and Trp264 are quenched by iron and account for almost the entire fluorescent signal when iron is released. As for the wild-type N-lobe, the fluorescence increase for each of these mutants is best fit by a double-exponential function indicating two processes. Trp8 is severely quenched under all conditions, making virtually no contribution to the signal. Additionally, a mutant lacking all three Trp residues allows assignment of the fluorescent signal completely to the three tryptophan residues and observation of the presence of one (or more) tyrosinates in the N-lobe that have physiological significance in the uptake of iron.
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Affiliation(s)
- Nicholas G James
- Department of Biochemistry, University of Vermont, Burlington, Vermont 05405, USA
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19
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Wong AYK, Hewitt J, Clarke BJ, Hudson DM, Krisinger MJ, Dower NA, MacGillivray RTA. Severe prothrombin deficiency caused by prothrombin-Edmonton (R-4Q) combined with a previously undetected deletion. J Thromb Haemost 2006; 4:2623-8. [PMID: 17002658 DOI: 10.1111/j.1538-7836.2006.02235.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND During infancy, a male patient experienced several life-threatening bleeding episodes. Standard coagulation tests revealed that the patient's plasma prothrombin activity was 8%, while his father's and mother's levels were 74% and 62%, respectively. OBJECTIVES A molecular genetic approach was used to determine the molecular basis of prothrombin deficiency within the family. PATIENT/METHODS Prothrombin genomic DNA fragments were amplified by using the polymerase chain reaction (PCR). In addition, liver cDNA fragments were amplified from the patient by using reverse transcription (RT) and PCR. The nucleotide sequences of the DNA fragments were determined. RESULTS A novel, heterozygous point mutation (g.1755 G > A, named prothrombin-Edmonton) was detected in the patient and his mother, resulting in the mutation of Arg-4 in the prothrombin propeptide to Gln (R-4Q). RT-PCR analysis of the patient's liver sample demonstrated the presence of two mRNA transcripts that differed by the presence or absence of exon 11. Real-time PCR analysis on genomic DNA and cDNA confirmed a deletion (g.10435_10809del) in the paternal allele. CONCLUSIONS The patient has a maternally-inherited point mutation (R-4Q) and a paternally-inherited deletion. By analogy with the previously reported factor IX San Dimas, the R-4Q mutation probably causes under-carboxylation of prothrombin and poor cleavage of the propeptide in the hepatocyte. The deletion probably results in a polypeptide that lacks 50 amino acids from the protease domain; this is likely to impair folding, secretion, stability and/or activity of the truncated prothrombin. The two mutations combine to give the prothrombin deficiency observed in the patient.
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Affiliation(s)
- A Y K Wong
- Centre for Blood Research and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
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20
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Hewitt J, Wong AYK, Wadsworth LD, MacGillivray RTA. Germline mutation identified after amplification of nuclear DNA from citrated plasma. Br J Haematol 2006; 136:171-2. [PMID: 17096685 DOI: 10.1111/j.1365-2141.2006.06401.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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21
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Byrne SL, Leverence R, Klein JS, Giannetti AM, Smith VC, MacGillivray RTA, Kaltashov IA, Mason AB. Effect of glycosylation on the function of a soluble, recombinant form of the transferrin receptor. Biochemistry 2006; 45:6663-73. [PMID: 16716077 DOI: 10.1021/bi0600695] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Production of the soluble portion of the transferrin receptor (sTFR) by baby hamster kidney (BHK) cells is described, and the effect of glycosylation on the biological function of sTFR is evaluated for the first time. The sTFR (residues 121-760) has three N-linked glycosylation sites (Asn251, Asn317, and Asn727). Although fully glycosylated sTFR is secreted into the tissue culture medium ( approximately 40 mg/L), no nonglycosylated sTFR could be produced, suggesting that carbohydrate is critical to the folding, stability, and/or secretion of the receptor. Mutants in which glycosylation at positions 251 and 727 (N251D and N727D) is eliminated are well expressed, whereas production of the N317D mutant is poor. Analysis by electrospray ionization mass spectrometry confirms dimerization of the sTFR and the absence of the carbohydrate at the single site in each mutant. The effect of glycosylation on binding to diferric human transferrin (Fe(2) hTF), an authentic monoferric hTF with iron in the C-lobe (designated Fe(C) hTF), and a mutant (designated Mut-Fe(C) hTF that features a 30-fold slower iron release rate) was determined by surface plasmon resonance; a small ( approximately 20%) but consistent difference is noted for the binding of Fe(C) hTF and the Mut-Fe(C) hTF to the sTFR N317D mutant. The rate of iron release from Fe(C) hTF and Mut-Fe(C) hTF in complex with the sTFR and the sTFR mutants at pH 5.6 reveals that only the N317D mutant has a significant effect. The carbohydrate at position 317 lies close to a region of the TFR previously shown to interact with hTF.
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Affiliation(s)
- Shaina L Byrne
- Department of Biochemistry, University of Vermont College of Medicine, Burlington, Vermont 05405-0068, USA
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22
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Abstract
Serine proteases of the chymotrypsin family show a dichotomous amino acid distribution for residue 225. Enzymes carrying Tyr at position 225 are activated by Na(+), whereas those carrying Pro are devoid of Na(+) binding and activation. Previous studies have demonstrated that the Y225P conversion is sufficient to abrogate Na(+) activation in several enzymes. However, the reverse substitution P225Y is necessary but not sufficient to introduce Na(+) binding and activation. Here we report that Streptomyces griseus trypsin, carrying Pro-225, can be engineered into a Na(+)-activated enzyme by replacing residues in the 170, 186, and 220 loops to those of coagulation factor Xa. The findings represent the first instance of an engineered Na(+)-activated enzyme and a proof of principle that should enable the design of other proteases with enhanced catalytic activity and allosteric regulation mediated by monovalent cation binding.
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Affiliation(s)
- Michael J Page
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Box 8231, St. Louis, Missouri 63110, USA
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23
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Abstract
With the completion of the human genome sequence, it is now possible to analyze the many individual components that comprise complex biologic systems. Despite this sequence data, understanding the biologic relationships of all proteins of a given cell or biologic sample (the proteome) is still an exceedingly difficult task. However, new technology developments mean that proteomics research can be used to investigate a variety of biologic systems. Already, these studies have given valuable insight for the development of improved diagnostic and therapeutic products. The present review aims to provide a basic understanding of proteomics research by discussing the methods used to study large numbers of proteins and by reviewing the application of proteomics methods to transfusion medicine.
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Affiliation(s)
- Michael J Page
- Department of Biochemistry and Molecular Biology, Centre for Blood Research, University of British Columbia, Vancouver, Canada
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24
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Vottero E, Mitchell DA, Page MJ, MacGillivray RTA, Sadowski IJ, Roberge M, Mauk AG. Cytochromeb5is a major reductant in vivo of human indoleamine 2,3-dioxygenase expressed in yeast. FEBS Lett 2006; 580:2265-8. [PMID: 16574111 DOI: 10.1016/j.febslet.2006.03.034] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Revised: 03/08/2006] [Accepted: 03/08/2006] [Indexed: 11/19/2022]
Abstract
The evolutionary relationship of indoleamine 2,3-dioxygenase (IDO) to some gastropod myoglobins suggests that IDO may undergo autoxidation in vivo such that one or more currently unidentified electron donors are required to maintain IDO heme iron in the active, ferrous state. To evaluate this hypothesis we have used yeast knockout mutants in combination with a recently developed yeast growth assay for IDO activity in vivo to demonstrate a role for cytochrome b(5) and cytochrome b(5) reductase in maintaining IDO activity in vivo.
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Affiliation(s)
- Eduardo Vottero
- Department of Biochemistry and Molecular Biology, Life Sciences Centre, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
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25
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Halbrooks PJ, Giannetti AM, Klein JS, Björkman PJ, Larouche JR, Smith VC, MacGillivray RTA, Everse SJ, Mason AB. Composition of pH-sensitive triad in C-lobe of human serum transferrin. Comparison to sequences of ovotransferrin and lactoferrin provides insight into functional differences in iron release. Biochemistry 2006; 44:15451-60. [PMID: 16300393 DOI: 10.1021/bi0518693] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The transferrins (TF) are a family of bilobal glycoproteins that tightly bind ferric iron. Each of the homologous N- and C-lobes contains a single iron-binding site situated in a deep cleft. Human serum transferrin (hTF) serves as the iron transport protein in the blood; circulating transferrin binds to receptors on the cell surface, and the complex is internalized by endocytosis. Within the cell, a reduction in pH leads to iron release from hTF in a receptor-dependent process resulting in a large conformational change in each lobe. In the hTF N-lobe, two critical lysines facilitate this pH-dependent conformational change allowing entry of a chelator to capture the iron. In the C-lobe, the lysine pair is replaced by a triad of residues: Lys534, Arg632, and Asp634. Previous studies show that mutation of any of these triad residues to alanine results in significant retardation of iron release at both pH 7.4 and pH 5.6. In the present work, the role of the three residues is probed further by conversion to the residues observed at the equivalent positions in ovotransferrin (Q-K-L) and human lactoferrin (K-N-N) as well as a triad with an interchanged lysine and arginine (K534R/R632K). As expected, all of the constructs bind iron and associate with the receptor with nearly the same K(D) as the wild-type monoferric hTF control. However, interesting differences in the effect of the substitutions on the iron release rate in the presence and absence of the receptor at pH 5.6 are observed. Additionally, titration with KCl indicates that position 632 must have a positively charged residue to elicit a robust rate acceleration as a function of increasing salt. On the basis of these observations, a model for iron release from the hTF C-lobe is proposed. These studies provide insight into the importance of charge and geometry of the amino acids at these positions as a partial explanation for differences in behavior of individual TF family members, human serum transferrin, ovotransferrin, and lactoferrin. The studies collectively highlight important features common to both the N- and C-lobes of TF and the critical role of the receptor in iron release.
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Affiliation(s)
- Peter J Halbrooks
- Department of Biochemistry, University of Vermont, College of Medicine, Burlington, Vermont 05405, USA
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26
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Teh EM, Hewitt J, Ung KC, Griffiths TAM, Nguyen V, Briggs SK, Mason AB, MacGillivray RTA. Identification of the epitope of a monoclonal antibody that disrupts binding of human transferrin to the human transferrin receptor. FEBS J 2006; 272:6344-53. [PMID: 16336271 DOI: 10.1111/j.1742-4658.2005.05028.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The molecular basis of the transferrin (TF)-transferrin receptor (TFR) interaction is not known. The C-lobe of TF is required to facilitate binding to the TFR and both the N- and C-lobes are necessary for maximal binding. Several mAb have been raised against human transferrin (hTF). One of these, designated F11, is specific to the C-lobe of hTF and does not recognize mouse or pig TF. Furthermore, mAb F11 inhibits the binding of TF to TFR on HeLa cells. To map the epitope for mAb F11, constructs spanning various regions of hTF were expressed as glutathione S-transferase (GST) fusion proteins in Escherichia coli. The recombinant fusion proteins were analysed in an iterative fashion by immunoblotting using mAb F11 as the probe. This process resulted in the localization of the F11 epitope to the C1 domain (residues 365-401) of hTF. Subsequent computer modelling suggested that the epitope is probably restricted to a surface patch of hTF consisting of residues 365-385. Mutagenesis of the F11 epitope of hTF to the sequence of either mouse or pig TF confirmed the identity of the epitope as immunoreactivity was diminished or lost. In agreement with other studies, these epitope mapping studies support a role for residues in the C1 domain of hTF in receptor binding.
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Affiliation(s)
- Evelyn M Teh
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, Canada
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27
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Griffiths TAM, Mauk AG, MacGillivray RTA. Recombinant Expression and Functional Characterization of Human Hephaestin: A Multicopper Oxidase with Ferroxidase Activity. Biochemistry 2005; 44:14725-31. [PMID: 16274220 DOI: 10.1021/bi051559k] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human hephaestin (Hp) is a transmembrane protein that has been implicated in duodenal iron export. Mutations in the murine hephaestin gene (sla) produce microcytic, hypochromic anemia that is refractory to oral iron therapy. Hp shares approximately 50% sequence identity with the plasma multicopper ferroxidase ceruloplasmin including conservation of residues involved in disulfide bond formation and metal coordination. On the basis of this similarity to ceruloplasmin, human hephaestin may also bind copper and possess ferroxidase activity. To test this hypothesis, human hephaestin cDNA has been cloned by reverse transcription of human duodenal mRNA. Following in vitro mutagenesis to make the encoded polypeptide suitable for expression and purification, the hephaestin cDNA was cloned into the expression vector pNUT and introduced into baby hamster kidney cells. After selection with methotrexate, the baby hamster kidney cells secreted the recombinant human hephaestin into the medium at a level of approximately 2 mg/L. Purification was achieved by a single immunoaffinity chromatography step. As judged by SDS-PAGE, N-terminal sequence analysis, and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, the purified hephaestin was homogeneous with a mass of 129600 Da, suggesting a carbohydrate content of 7.7%. Inductively coupled plasma mass spectrometry revealed that recombinant hephaestin contained an average of 3.13 atoms of copper per protein molecule. A visible absorption maximum was observed at 607 nm, consistent with the presence of a Type 1 copper site. By using ferrous ammonium sulfate as a substrate, recombinant hephaestin was shown to have ferroxidase activity with a K(m) of 2.1 microM for Fe(II). Lastly, urea PAGE showed that hephaestin was able to catalyze formation of diferric transferrin from Fe(II) and apotransferrin.
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Affiliation(s)
- Tanya A M Griffiths
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
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28
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Mason AB, Halbrooks PJ, James NG, Connolly SA, Larouche JR, Smith VC, MacGillivray RTA, Chasteen ND. Mutational analysis of C-lobe ligands of human serum transferrin: insights into the mechanism of iron release. Biochemistry 2005; 44:8013-21. [PMID: 15924420 DOI: 10.1021/bi050015f] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Each homologous lobe of human serum transferrin (hTF) has one Fe(3+) ion bound by an aspartic acid, a histidine, two tyrosine residues, and two oxygens from the synergistic anion, carbonate. Extensive characterization of these ligands in the N-terminal lobe has been carried out. Despite sharing the same set of ligands, there is a substantial amount of evidence that the N- and C-lobes are inequivalent. Studies of full-length hTF have shown that iron release from each lobe is kinetically distinguishable. To simplify the assessment of mutations in the C-lobe, we have created mutant hTF molecules in which the N-lobe binds iron with high affinity or not at all. Mutations targeting the C-lobe liganding residues have been introduced into these hTF constructs. UV-visible spectral, kinetic, and EPR studies have been undertaken to assess the effects of each mutation and to allow direct comparison to the N-lobe. As found for the N-lobe, the presence of Y517 in the C-lobe (equivalent to Y188 in the N-lobe) is absolutely essential for the binding of iron. Unlike the N-lobe, however, mutation of Y426 (equivalent to Y95) does not produce a stable complex with iron. For the mutants that retain the ability to bind iron (D392S and H585A), the rates of release are considerably slower than those measured for equivalent mutations in the N-lobe at both pH 7.4 and pH 5.6. Equilibrium binding experiments with HeLa S(3) cells indicate that recombinant hTF, in which Y426 or H585 is mutated, favor a closed or nearly closed conformation while those with mutations of the D392 or Y517 ligands appear to promote an open conformation. The differences in the effects of mutating the liganding residues in the two lobes and the subtle indications of cooperativity between lobes point to the importance of the transferrin receptor in effecting iron release from the C-lobe. Significantly, the equilibrium binding experiments also indicate that, regardless of which lobe contains the iron, the free energy of binding is equivalent and not additive; each monoferric hTF has a free energy of binding that is 82% of diferric hTF.
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Affiliation(s)
- Anne B Mason
- Department of Biochemistry, University of Vermont College of Medicine, Burlington, Vermont 05405-0068, USA.
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29
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Hewitt J, Ballard JNM, Nelson TN, Smith VC, Griffiths TAM, Pritchard S, Wu JK, Wadsworth LD, Casey B, MacGillivray RTA. Confirmation of paternity suggests a new mutation in the factor VII gene: 'Pater certus quouque est' - Response to Girolami et al. Br J Haematol 2005. [DOI: 10.1111/j.1365-2141.2005.05624.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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30
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Hewitt J, Ballard JNM, Nelson TN, Smith VC, Griffiths TAM, Pritchard S, Wu JK, Wadsworth LD, Casey B, MacGillivray RTA. Severe FVII deficiency caused by a new point mutation combined with a previously undetected gene deletion. Br J Haematol 2005; 128:380-5. [PMID: 15667541 DOI: 10.1111/j.1365-2141.2004.05296.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A 3-week-old Caucasian female presented with severe unprovoked parenchymal cerebral haemorrhage. Her plasma factor VII (FVII) activity was <0.01 units/ml. FVII activities for her mother and sister were 0.65 units/ml and 0.51 units/ml, respectively, while her father's level was normal. These results indicated that the mother was heterozygous for a non-functional F7 gene that had also been inherited by the proband's sister. The proband's severe FVII deficiency was caused by a new mutation in her paternal F7 gene coupled with the inheritance of the non-functional maternal F7 gene. DNA sequence analysis revealed that the proband had apparent homozygosity for a novel single point mutation (g.3907G >A) changing the codon for Glu29 to Lys (E29K); neither parent had the E29K mutation. Because of the unlikelihood that the proband was homozygous for two identical new point mutations, the DNA sequence abnormality was more likely to have arisen from a single mutated gene on one allele and a F7 gene deletion on the other allele. Real time polymerase chain reaction (PCR) analysis confirmed that the proband had inherited a gene deletion that was present in the maternal side of the family. Subsequent clotting assays and real time PCR revealed that the maternal deletion also included the closely linked F10 gene.
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Affiliation(s)
- Jeff Hewitt
- Department of Biochemistry and Molecular Biology, University of Bristish Columbia, Vancouver, Canada
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31
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Mason AB, Halbrooks PJ, Larouche JR, Briggs SK, Moffett ML, Ramsey JE, Connolly SA, Smith VC, MacGillivray RTA. Expression, purification, and characterization of authentic monoferric and apo-human serum transferrins. Protein Expr Purif 2005; 36:318-26. [PMID: 15249056 DOI: 10.1016/j.pep.2004.04.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2004] [Revised: 04/12/2004] [Indexed: 11/17/2022]
Abstract
Transferrin is a bilobal protein with the ability to bind iron in two binding sites situated at the bottom of a cleft in each lobe. We have previously described the production of recombinant non-glycosylated human serum transferrins (hTF-NG), containing a factor Xa cleavage site and a hexa-His tag at the amino-terminus. Constructs in this background that contain strategic mutations to completely prevent iron binding in each lobe or in both lobes have now been produced. These monoferric hTFs will allow dissection of the contribution of each lobe to transferrin function. In addition, the construct completely lacking in the ability to bind iron in either lobe provides an opportunity to assess whether hTF has any other functions in addition to iron transport. Following insertion of the His-tagged hTF molecules into the pNUT vector, transfection into baby hamster kidney cells and selection with methotrexate, the secreted recombinant proteins were isolated from the tissue culture medium and characterized with regard to their iron binding properties. Significant improvements over our previous protocol include: (1) addition of butyric acid at a level of 1mM which leads to a substantial increase in protein production (as much as a 65% increase compared to control cells); and (2) elimination of an anion exchange column prior to isolation on a Qiagen Ni-NTA column which makes purification of the His-tagged constructs faster and therefore more efficient. These improvements should be applicable to expression of other recombinant proteins in mammalian cells.
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Affiliation(s)
- Anne B Mason
- Department of Biochemistry, University of Vermont, College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405, USA.
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32
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Abstract
The fbpABC operon in Neisseria gonorrhoeae encodes an ATP-binding cassette transporter required for iron uptake from the host ferric binding proteins. The gene for the nucleotide-binding domain (fbpC) expressed in Escherichia coli has intrinsic ATPase activity (0.5 mmol/min/mg) uncoupled from the iron transport process. The FbpC E164D mutant is found to have a 10-fold reduction in specific activity. FbpC is covalently modified by 8-azido-[gamma32P]ATP, indicating that FbpC is a functional ATPase that likely combines with FbpB to form a ferric iron transporter.
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Affiliation(s)
- Gloria H Y Lau
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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33
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Abstract
Streptomyces griseus trypsin (SGT) was chosen as a model scaffold for the development of serine proteases with enhanced substrate specificity. Recombinant SGT has been produced in a Bacillus subtilis expression system in a soluble active form and purified to homogeneity. The recombinant and native proteases have nearly identical enzymatic properties and structures. Four SGT mutants with alterations in the S1 substrate binding pocket (T190A, T190P, T190S, and T190V) were also expressed. The T190P mutant demonstrated the largest shift to a preference for Arg versus Lys in the P1 site. This was shown by a minor reduction in catalytic activity toward an Arg-containing substrate (k(cat) reduction of 25%). The crystal structures of the recombinant SGT and the T190P mutant in a complex with the inhibitor benzamidine were obtained at high resolution (approximately 1.9 A). The increase in P1 specificity, achieved with minimal effect on the catalytic efficiency, demonstrates that the T190P mutant is an ideal candidate for the design of additional substrate specificity engineered into the S2 to S4 binding pockets.
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Affiliation(s)
- Michael J Page
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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Halbrooks PJ, He QY, Briggs SK, Everse SJ, Smith VC, MacGillivray RTA, Mason AB. Investigation of the mechanism of iron release from the C-lobe of human serum transferrin: mutational analysis of the role of a pH sensitive triad. Biochemistry 2003; 42:3701-7. [PMID: 12667060 DOI: 10.1021/bi027071q] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The transferrins (TFs) are a family of proteins that are widely distributed in vertebrates, where they serve a major role in iron binding and transport. Most TFs are composed of two homologous lobes, the N- and C-lobes, each able to bind a single iron atom. Human serum transferrin (hTF) binds iron in the blood and delivers it to actively dividing cells; through the process of receptor-mediated endocytosis, diferric hTF in the serum (pH approximately 7.4) binds to specific TF receptors on the cell surface and is internalized, whereupon a pH drop in the endosome (pH approximately 5.6) facilitates iron release. Many factors affect the rate of iron release, including pH, chelator, temperature, salt, and lobe-lobe interactions. We, and others, have actively studied the mechanism of iron release from the recombinant N-lobe of hTF; in contrast, the exact details of iron release from the C-lobe have remained less well characterized but appear to differ from those found for the N-lobe. Recently, to simplify the purification protocol, we have expressed and purified full-length recombinant hTF containing an N-terminal hexahistidine tag [Mason et al. (2002) Biochemistry 41, 9448-9454]. In the present work, we have expressed a full-length recombinant hTF containing a K206E mutation such that the N-lobe does not readily release iron. The resulting full-length hTF allows us to focus on the C-lobe and to study the effects of mutations introduced into the C-lobe. The success of this strategy is documented and in vitro mutagenesis is used to identify three residues in the C-lobe that are critical for iron-release. Although the importance of this triad is unequivocally demonstrated, further studies are needed to completely elucidate the mechanism of iron release from the C-lobe of hTF. In addition, the striking difference in the effect of increasing salt concentrations on iron release from the two lobes of hTF is further documented in the present work.
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Affiliation(s)
- Peter J Halbrooks
- Department of Biochemistry, University of Vermont, College of Medicine, 89 Beaumont Avenue, Burlington, Vermont 05405, USA
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Adams TE, Mason AB, He QY, Halbrooks PJ, Briggs SK, Smith VC, MacGillivray RTA, Everse SJ. The position of arginine 124 controls the rate of iron release from the N-lobe of human serum transferrin. A structural study. J Biol Chem 2003; 278:6027-33. [PMID: 12458193 DOI: 10.1074/jbc.m210349200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human serum transferrin (hTF) is a bilobal iron-binding and transport protein that carries iron in the blood stream for delivery to cells by a pH-dependent mechanism. Two iron atoms are held tightly in two deep clefts by coordination to four amino acid residues in each cleft (two tyrosines, a histidine, and an aspartic acid) and two oxygen atoms from the "synergistic" carbonate anion. Other residues in the binding pocket, not directly coordinated to iron, also play critical roles in iron uptake and release through hydrogen bonding to the liganding residues. The original crystal structures of the iron-loaded N-lobe of hTF (pH 5.75 and 6.2) revealed that the synergistic carbonate is stabilized by interaction with Arg-124 and that both the arginine and the carbonate adopt two conformations (MacGillivray, R. T. A., Moore, S. A., Chen, J., Anderson, B. F., Baker, H., Luo, Y. G., Bewley, M., Smith, C. A., Murphy, M. E., Wang, Y., Mason, A. B., Woodworth, R. C., Brayer, G. D., and Baker, E. N. (1998) Biochemistry 37, 7919-7928). In the present study, we show that the two conformations are also found for a structure at pH 7.7, indicating that this finding was not strictly a function of pH. We also provide structures for two single point mutants (Y45E and L66W) designed to force Arg-124 to adopt each of the previously observed conformations. The structures of each mutant show that this goal was accomplished, and functional studies confirm the hypothesis that access to the synergistic anion dictates the rate of iron release. These studies highlight the importance of the arginine/carbonate movement in the mechanism of iron release in the N-lobe of hTF. Access to the carbonate via a water channel allows entry of protons and anions, enabling the attack on the iron.
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Affiliation(s)
- Ty E Adams
- Department of Biochemistry, University of Vermont, College of Medicine, Burlington, Vermont 05405, USA
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Guo M, Harvey I, Yang W, Coghill L, Campopiano DJ, Parkinson JA, MacGillivray RTA, Harris WR, Sadler PJ. Synergistic anion and metal binding to the ferric ion-binding protein from Neisseria gonorrhoeae. J Biol Chem 2003; 278:2490-502. [PMID: 12372824 DOI: 10.1074/jbc.m208776200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 34-kDa periplasmic iron-transport protein (FBP) from Neisseria gonorrhoeae (nFBP) contains Fe(III) and (hydrogen)phosphate (synergistic anion). It has a characteristic ligand-to-metal charge-transfer absorption band at 481 nm. Phosphate can be displaced by (bi)carbonate to give Fe.CO(3).nFBP (lambda(max) 459 nm). The local structures of native Fe-PO(4)-nFBP and Fe.CO(3).nFBP were determined by EXAFS at the FeK edge using full multiple scattering analysis. The EXAFS analysis reveals that both phosphate and carbonate ligands bind to FBP in monodentate mode in contrast to transferrins, which bind carbonate in bidentate mode. The EXAFS analysis also suggests an alternative to the crystallographically determined position of the Glu ligand, and this in turn suggests that an H-bonding network may help to stabilize monodentate binding of the synergistic anion. The anions oxalate, pyrophosphate, and nitrilotriacetate also appear to serve as synergistic anions but not sulfate or perchlorate. The oxidation of Fe(II) in the presence of nFBP led to a weak Fe(III).nFBP complex (lambda(max) 471 nm). Iron and phosphate can be removed from FBP at low pH (pH 4.5) in the presence of a large excess of citrate. Apo-FBP is less soluble and less stable than Fe.nFBP and binds relatively weakly to Ga(III) and Bi(III) but not to Co(III) ions, all of which bind strongly to apo-human serum transferrin.
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Affiliation(s)
- Maolin Guo
- School of Chemistry, University of Edinburgh, United Kingdom
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Mason AB, He QY, Halbrooks PJ, Everse SJ, Gumerov DR, Kaltashov IA, Smith VC, Hewitt J, MacGillivray RTA. Differential effect of a his tag at the N- and C-termini: functional studies with recombinant human serum transferrin. Biochemistry 2002; 41:9448-54. [PMID: 12135367 DOI: 10.1021/bi025927l] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Attachment of a cleavable hexa His tag is a common strategy for the production of recombinant proteins. Production of two recombinant nonglycosylated human serum transferrins (hTF-NG), containing a factor Xa cleavage site and a hexa His tag at the carboxyl terminus, has been described [Mason et al. (2001) Prot. Exp. Purif 23, 142-150]. More recently, hTF-NG with an amino-terminal His tag and a factor Xa cleavage site has been expressed (>30 mg/L) in baby hamster kidney cells and purified from the tissue culture medium. Although it is frequently assumed that addition of a His tag has little or no effect on function, this is not always confirmed experimentally. In the present study, in vitro quantitative data clearly shows that the presence of the C-terminal His tag has an effect on the release of iron from recombinant hTF at pH 7.4 and 5.6. Measurement of the rate of release from both the N- and C-lobes is reduced 2-4-fold. These findings provide further compelling evidence that the two lobes communicate with each other and highlight the importance of the C-terminal portion of the C-terminal lobe in this interaction. In contrast to these results, we demonstrate that the presence of a His tag at the N-terminus of hTF has no effect on the rate of iron release from either lobe. In a competition experiment, both unlabeled N- and C-terminal His-tagged constructs were equally effective at inhibiting the binding of radio-iodinated diferric glycosylated hTF from a commercial source to receptors on HeLa cells as the unlabeled recombinant diferric hTF-NG control. Thus, the presence of a His tag at either the N- or C-terminus of hTF-NG has no apparent effect on the ability of these hTF species to bind to transferrin receptors.
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Affiliation(s)
- Anne B Mason
- Department of Biochemistry, University of Vermont, College of Medicine, Burlington, Vermont 05405, USA.
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Jacobs BA, Mauk MR, Funk WD, MacGillivray RTA, Mauk AG, Gray HB. Preparation, characterization, and intramolecular electron transfer in pentaammineruthenium histidine-26 cytochrome b5 derivatives: role of the intervening medium in long-range donor-acceptor electronic coupling. J Am Chem Soc 2002. [DOI: 10.1021/ja00012a003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Morrow GW, Kieffer TJ, McIntosh CHS, MacGillivray RTA, Brown JC, St-Pierre S, Pederson RA. The insulinotropic region of gastric inhibitory polypeptide; fragment analysis suggests the bioactive site lies between residues 19 and 30. Can J Physiol Pharmacol 1996. [DOI: 10.1139/y95-229] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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