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Thesbjerg MN, Sundekilde UK, Poulsen NA, Larsen LB, Nielsen SDH. A novel proteomic approach for the identification and relative quantification of disulfide-bridges in the human milk proteome. J Proteomics 2024; 301:105194. [PMID: 38723850 DOI: 10.1016/j.jprot.2024.105194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 04/26/2024] [Accepted: 05/05/2024] [Indexed: 05/13/2024]
Abstract
This study explores the disulfide bridges present in the human milk proteome by a novel approach permitting both positional identification and relative quantification of the disulfide bridges. Human milk from six donors was subjected to trypsin digestion without reduction. The digested human milk proteins were analyzed by nanoLC-timsTOF Pro combined with data analysis using xiSEARCH. A total of 85 unique disulfide bridges were identified in 25 different human milk proteins. The total relative abundance of disulfide bridge-containing peptides constituted approximately 5% of the total amount of tryptic-peptides. Seven inter-molecular disulfide bridges were identified between either α-lactalbumin and lactotransferrin (5) or αS1-casein and κ-casein (2). All cysteines involved in the observed disulfide bridges of α-lactalbumin and lactotransferrin were mapped onto protein models using AlphaFold2 Multimer to estimate the length of the observed disulfide bridges. The lengths of the disulfide bridges of lactotransferrin indicate a potential for multi- or poly-merization of lactotransferrin. The high number of intramolecular lactotransferrin disulfide bridges identified, suggests that these are more heterogeneous than previously presumed. SIGNIFICANCE: Disulfide-bridges in the human milk proteome are an often overseen post-transaltional modification. Thus, mapping the disulfide-bridges, their positions and relative abundance, are valuable new knowledge needed for an improved understanding of human milk protein behaviour. Although glycosylation and phosphorylation have been described, even less information is available on the disulfide bridges and the disulfide-bridge derived protein complexes. This is important for future work in precision fermentation for recombinant production of human milk proteins, as this will highlight which disulfide-bridges are naturally occouring in human milk proteins. Further, this knowledge would be of value for the infant formula industry as it provides more information on how to humanize bovine-milk based infant formula. The novel method developed here can be broadly applied in other biological systems as the disulfid-brigdes are important for the structure and functionality of proteins.
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Affiliation(s)
- Martin Nørmark Thesbjerg
- Department of Food Science, Aarhus University, Agro Food Park 48, DK-8200 Aarhus N, Denmark; Sino-Danish College (SDC), University of Chinese Academy of Science, Huairou District, Beijing 101408, China.
| | | | - Nina Aagaard Poulsen
- Department of Food Science, Aarhus University, Agro Food Park 48, DK-8200 Aarhus N, Denmark
| | - Lotte Bach Larsen
- Department of Food Science, Aarhus University, Agro Food Park 48, DK-8200 Aarhus N, Denmark
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Honarparvar B, Kanchi S, Bisetty K. Theoretical insights into the competitive metal bioaffinity of lactoferrin as a metal ion carrier: a DFT study. NEW J CHEM 2019. [DOI: 10.1039/c9nj03786a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Metal–protein complexes, specifically lactoferrin (Lf), an iron-binding glycoprotein found naturally in milk and several other body fluids play a pivotal role in all living organisms.
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Affiliation(s)
- Bahareh Honarparvar
- Department of Chemistry
- Durban University of Technology
- Durban 4000
- South Africa
| | - Suvardhan Kanchi
- Department of Chemistry
- Durban University of Technology
- Durban 4000
- South Africa
| | - Krishna Bisetty
- Department of Chemistry
- Durban University of Technology
- Durban 4000
- South Africa
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3
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Chen HA, Chiu CC, Huang CY, Chen LJ, Tsai CC, Hsu TC, Tzang BS. Lactoferrin Increases Antioxidant Activities and Ameliorates Hepatic Fibrosis in Lupus-Prone Mice Fed with a High-Cholesterol Diet. J Med Food 2016; 19:670-7. [PMID: 27332506 DOI: 10.1089/jmf.2015.3634] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Lactoferrin (LF) has beneficial effects against various diseases. However, the effects of LF on liver fibrosis in systematic lupus erythematosus (SLE) are unknown. In this study, NZB/W F1 mice were utilized to investigate the effects of LF on SLE. Experiments reveal that LF significantly increases glutathione and 1,1-diphenyl-2-picryl-hydrazyl levels and significantly decreased malondialdehyde levels in both serum and liver in NZB/W F1 mice. LF also lowered matrix metalloproteinase-9 activity and liver inflammatory indices, such as aminotransferase and alanine aminotransferase. Notably, significantly decreased expression of fibrotic related molecules, including transforming growth factor (TGF)-β1, tumor necrosis factor-α, interleukin-1β, and TGF-β1 receptor, were observed in the livers of NZB/W F1 mice that had been treated with LF. Significantly, suppressed Smad2/3 signaling, α-smooth muscle actin, and collagen deposition were also detected. These findings reveal that LF has beneficial effects on SLE by increasing antioxidant activities and ameliorating liver inflammation and fibrosis, suggesting the therapeutic effectiveness of LF against SLE.
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Affiliation(s)
- Hung-An Chen
- 1 Division of Allergy-Immunology-Rheumatology, Department of Internal Medicine, Chi-Mei Medical Center , Tainan, Taiwan
| | - Chun-Ching Chiu
- 2 Department of Neurology, Chunghua Christian Hospital , Chunghua, Taiwan .,3 Department of Medical Intensive Care Unit, Chunghua Christian Hospital , Chunghua, Taiwan
| | - Chih-Yang Huang
- 4 Graduate Institute of Basic Medical Science, China Medical University , Taichung, Taiwan .,5 Graduate Institute of Chinese Medical Science, China Medical University , Taichung, Taiwan .,6 Department of Health and Nutrition Biotechnology, Asia University , Taichung, Taiwan
| | - Li-Jeng Chen
- 7 Institute of Biochemistry, Microbiology and Immunology, School of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Chun-Chou Tsai
- 7 Institute of Biochemistry, Microbiology and Immunology, School of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Tsai-Ching Hsu
- 7 Institute of Biochemistry, Microbiology and Immunology, School of Medicine, Chung Shan Medical University, Taichung, Taiwan .,Immunology Research Center, School of Medicine, Chung Shan Medical University, Taichung, Taiwan .,Clinical Laboratory, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Bor-Show Tzang
- 7 Institute of Biochemistry, Microbiology and Immunology, School of Medicine, Chung Shan Medical University, Taichung, Taiwan .,Immunology Research Center, School of Medicine, Chung Shan Medical University, Taichung, Taiwan .,9 Department of Biochemistry, School of Medicine, Chung Shan Medical University, Taichung, Taiwan .,Clinical Laboratory, Chung Shan Medical University Hospital, Taichung, Taiwan
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4
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Hata T, Shibata Y, Okano M, Kodera A, Ueda M, Iwamoto H, Tomida H, Iwamoto H, Hirose J. Flexibility of the Coordination Geometry at the N-Site of Cu(II) 2 Human Serum-Transferrin Induced by the Different Orientations of Arg124. Biol Pharm Bull 2015; 38:358-64. [DOI: 10.1248/bpb.b13-00954] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Toshiyuki Hata
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University
| | - Yu Shibata
- Faculty of Life Science and Biotechnology, Fukuyama University
| | - Miku Okano
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University
| | - Asako Kodera
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University
| | - Misato Ueda
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University
| | - Hiroshi Iwamoto
- Faculty of Life Science and Biotechnology, Fukuyama University
| | - Hisao Tomida
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University
| | | | - Junzo Hirose
- Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University
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5
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Chen W, Ye D, Wang H, Lin D, Huang J, Sun H, Zhong W. Binding of oxo-Cu2 clusters to ferric ion-binding protein A from Neisseria gonorrhoeae: a structural insight. Metallomics 2014; 5:1430-9. [PMID: 23884152 DOI: 10.1039/c3mt00091e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ferric ion-binding protein A (FbpA), a member of transferrin superfamily, is a periplasmic iron transporter employed by many Gram-negative pathogens. Our experiments indicated copper(ii) could bind with Neisseria gonorrhoeae FbpA (NgFbpA), and the binding constant reached up to (8.7 ± 0.2) × 10(8) M(-1)via UV-vis titration. The crystal structure of recombinant Cu-NgFbpA at 2.1 Å revealed that the oxo-Cu2 clusters (dinuclear centres) assembled in the iron binding cleft and were bound to the two adjacent tyrosine residues (Y195 and Y196) of the protein, two Cu ions coordinated with two tyrosines, Y195 and Y196, respectively, which was different from the binding model of Fe ion with FbpA, in which Y195 and Y196 coordinated together with one Fe ion. While this was similar to the binding of Zr and Hf ion clusters, Y195 and Y196 coordinated with two metal ions and the μ-oxo-bridges linking the metal ions. Structural superimposition demonstrated that oxo-Cu2-NgFbpA still keeping an open conformation, similar to the apo-form of NgFbpA. The structure presented additional information towards an understanding of the function of FbpA, and provided a detailed binding model for FbpA protein with the possible metal ions in a biological system.
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Affiliation(s)
- Weijing Chen
- School of Pharmacy, Second Military Medical University, Shanghai, P. R. China.
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6
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Müh F, Zouni A. The nonheme iron in photosystem II. PHOTOSYNTHESIS RESEARCH 2013; 116:295-314. [PMID: 24077892 DOI: 10.1007/s11120-013-9926-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 09/17/2013] [Indexed: 06/02/2023]
Abstract
Photosystem II (PSII), the light-driven water:plastoquinone (PQ) oxidoreductase of oxygenic photosynthesis, contains a nonheme iron (NHI) at its electron acceptor side. The NHI is situated between the two PQs QA and QB that serve as one-electron transmitter and substrate of the reductase part of PSII, respectively. Among the ligands of the NHI is a (bi)carbonate originating from CO2, the substrate of the dark reactions of oxygenic photosynthesis. Based on recent advances in the crystallography of PSII, we review the structure of the NHI in PSII and discuss ideas concerning its function and the role of bicarbonate along with a comparison to the reaction center of purple bacteria and other enzymes containing a mononuclear NHI site.
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Mizutani K, Toyoda M, Mikami B. X-ray structures of transferrins and related proteins. Biochim Biophys Acta Gen Subj 2011; 1820:203-11. [PMID: 21855609 DOI: 10.1016/j.bbagen.2011.08.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 07/21/2011] [Accepted: 08/03/2011] [Indexed: 11/25/2022]
Abstract
BACKGROUND Transferrins are a group of iron-binding proteins including serum transferrin, lactoferrin and ovotransferrin. SCOPE OF REVIEW The structures of transferrins are discussed. GENERAL SIGNIFICANCE The typical transferrin molecules are folded into two homologous lobes. X-ray crystallography revealed that each lobe is further divided into two similarly sized domains, and that an iron-binding site is contained within the inter-domain cleft. The six iron coordination sites are occupied by four residues and a bidentate carbonate anion. MAJOR CONCLUSIONS The structures of the apo- and holo-forms revealed that the transferrins undergo a large-scale conformational change upon the uptake and release of irons: domains rotate as rigid bodies around a screw axis passing through inter-domain contacts. The iron-release mechanism of transferrin N-lobe is also revealed by X-ray crystallography; two basic residues in two domains form an unusual hydrogen bond in neutral pH, and the bond should be broken and facilitate iron release at a low pH of the endosome. For ovotransferrin, the iron release kinetics of two lobes correspond well with the numbers of anion binding sites found in crystal structures. The structures of transferrins bound to other metals revealed that the flexibility of the transferrin structure allows the ability to bind to other metals. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
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Affiliation(s)
- Kimihiko Mizutani
- Laboratory of Applied Structural Biology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
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Ahmed IAM, Young SD, Crout NMJ. Ageing and structural effects on the sorption characteristics of Cd2+ by clinoptilolite and Y-type zeolite studied using isotope exchange technique. JOURNAL OF HAZARDOUS MATERIALS 2010; 184:574-584. [PMID: 20843600 DOI: 10.1016/j.jhazmat.2010.08.074] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 08/13/2010] [Accepted: 08/19/2010] [Indexed: 05/29/2023]
Abstract
This research investigates the long-term kinetics of Cd(2+) sorption and desorption by calcium-exchanged clinoptilolite (CaCpt) and Y-type (CaY) zeolite using isotopic exchange with (109)Cd while maintaining pH at circumneutral values. The effects of Si/Al ratio and crystal structure of these zeolitic materials on intracrystalline transport of Cd are discussed. A first-order kinetic model was developed to describe the progressive transfer of Cd(2+) to a less reactive form within the zeolite structure, following initial sorption and subsequent desorption of Cd subject to different initial contact times. The kinetic model differentiates between two forms of sorbed Cd(2+) designated 'labile' and 'non-labile' in which the labile form is in immediate equilibrium with the free Cd(2+) ion activity in solution. A model combining diffusion and first-order kinetics for cation exchange was also employed to determine Cd(2+) diffusivity and intracrystalline exchange rates in CaY and CaCpt. The efficiency of Permeable Reactive Barriers (PRBs) containing zeolitic materials in protecting water systems against lateral flow of metal-contaminated leachate was simulated for three contrasting zeolites. The slow transfer of Cd between labile and non-labile forms was particularly important in moderating high concentration pulses of Cd traversing the PRB. In addition, the reversibility of Cd fixation effectively restored the sorption capability of the zeolite through slow leakage to drainage water.
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Affiliation(s)
- I A M Ahmed
- School of Biosciences, Division of Agriculture & Environmental Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
| | - S D Young
- School of Biosciences, Division of Agriculture & Environmental Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - N M J Crout
- School of Biosciences, Division of Agriculture & Environmental Sciences, University of Nottingham, Nottingham NG7 2RD, UK
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9
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Cremades E, Echeverría J, Alvarez S. The Trigonal Prism in Coordination Chemistry. Chemistry 2010; 16:10380-96. [DOI: 10.1002/chem.200903032] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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10
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Koike R, Kidera A, Ota M. Alteration of oligomeric state and domain architecture is essential for functional transformation between transferase and hydrolase with the same scaffold. Protein Sci 2009; 18:2060-6. [PMID: 19670211 DOI: 10.1002/pro.218] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Transferases and hydrolases catalyze different chemical reactions and express different dynamic responses upon ligand binding. To insulate the ligand molecule from the surrounding water, transferases bury it inside the protein by closing the cleft, while hydrolases undergo a small conformational change and leave the ligand molecule exposed to the solvent. Despite these distinct ligand-binding modes, some transferases and hydrolases are homologous. To clarify how such different catalytic modes are possible with the same scaffold, we examined the solvent accessibility of ligand molecules for 15 SCOP superfamilies, each containing both transferase and hydrolase catalytic domains. In contrast to hydrolases, we found that nine superfamilies of transferases use two major strategies, oligomerization and domain fusion, to insulate the ligand molecules. The subunits and domains that were recruited by the transferases often act as a cover for the ligand molecule. The other strategies adopted by transferases to insulate the ligand molecule are the relocation of catalytic sites, the rearrangement of secondary structure elements, and the insertion of peripheral regions. These findings provide insights into how proteins have evolved and acquired distinct functions with a limited number of scaffolds.
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11
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Echeverría J, Cremades E, Amoroso AJ, Alvarez S. Jahn–Teller distortions of six-coordinate CuII compounds: cis or trans? Chem Commun (Camb) 2009:4242-4. [DOI: 10.1039/b903867a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Kay CWM, Mkami HE, Cammack R, Evans RW. Pulsed ELDOR Determination of the Intramolecular Distance between the Metal Binding Sites in Dicupric Human Serum Transferrin and Lactoferrin. J Am Chem Soc 2007; 129:4868-9. [PMID: 17394319 DOI: 10.1021/ja068966j] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher W M Kay
- Department of Biology, University College London, Gower Street, London WC1E 6BT, UK.
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13
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Chakraborty S, Chakraborty N, Jain D, Salunke DM, Datta A. Active site geometry of oxalate decarboxylase from Flammulina velutipes: Role of histidine-coordinated manganese in substrate recognition. Protein Sci 2002; 11:2138-47. [PMID: 12192069 PMCID: PMC2373591 DOI: 10.1110/ps.0206802] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Oxalate decarboxylase (OXDC) from the wood-rotting fungus Flammulina velutipes, which catalyzes the conversion of oxalate to formic acid and CO(2) in a single-step reaction, is a duplicated double-domain germin family enzyme. It has agricultural as well as therapeutic importance. We reported earlier the purification and molecular cloning of OXDC. Knowledge-based modeling of the enzyme reveals a beta-barrel core in each of the two domains organized in the hexameric state. A cluster of three histidines suitably juxtaposed to coordinate a divalent metal ion exists in both the domains. Involvement of the two histidine clusters in the catalytic mechanism of the enzyme, possibly through coordination of a metal cofactor, has been hypothesized because all histidine knockout mutants showed total loss of decarboxylase activity. The atomic absorption spectroscopy analysis showed that OXDC contains Mn(2+) at up to 2.5 atoms per subunit. Docking of the oxalate in the active site indicates a similar electrostatic environment around the substrate-binding site in the two domains. We suggest that the histidine coordinated manganese is critical for substrate recognition and is directly involved in the catalysis of the enzyme.
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Affiliation(s)
- Subhra Chakraborty
- National Center for Plant Genome Research, Jawaharlal Nehru University Campus, New Delhi 110067, India
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Satué-Gracia MT, Frankel EN, Rangavajhyala N, German JB. Lactoferrin in infant formulas: effect on oxidation. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2000; 48:4984-4990. [PMID: 11052766 DOI: 10.1021/jf0002490] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Lactoferrin is an iron transport protein present in human milk at an average concentration of 1.4 mg/mL. Commercially modified infant formulas based on cow's milk contain much lower amounts of lactoferrin (0.1 mg/mL lactoferrin) and soy based formulas have none. In addition to its role in iron transport, lactoferrin has bacteriostatic and bactericidal activities. Infant formulas are supplemented with relatively large amounts of iron (up to 12 mg/L). The effect of various concentrations of added lactoferrin and supplemental iron on lipid oxidation was tested in two different infant formulas. The extent of oxidation in the formulas as a function of time was determined by formation of hydroperoxides, production of hexanal, and fluorescence. On the basis of all three of these determinations, lactoferrin acted as an antioxidant in the absence and presence of different concentrations of supplemented iron. Lactoferrin inhibited oxidation in a concentration-dependent manner even at concentrations beyond its capacity to bind iron at its two high affinity binding sites. Lactoferrin can be used, therefore, as a dual purpose additive in infant formulas and similar food products for its antioxidant and its antimicrobial properties.
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Affiliation(s)
- M T Satué-Gracia
- Department of Food Science and Technology, University of California, Davis, California 95616, USA
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Brownlow S, Morais Cabral JH, Cooper R, Flower DR, Yewdall SJ, Polikarpov I, North AC, Sawyer L. Bovine beta-lactoglobulin at 1.8 A resolution--still an enigmatic lipocalin. Structure 1997; 5:481-95. [PMID: 9115437 DOI: 10.1016/s0969-2126(97)00205-0] [Citation(s) in RCA: 600] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND beta-Lactoglobulin (beta-Lg) is the major whey protein in the milk of ruminants and many other mammals. Its function is not known, but it undergoes at least two pH-dependent conformational changes which may be important. Bovine beta-Lg crystallizes in several different lattices, and medium-resolution structures of orthorhombic lattice Y and trigonal lattice Z have been published. Triclinic lattice X and lattice Z crystals grow at pH values either side of the pH at which one of the pH-induced conformational changes occurs. A full understanding of the structure is needed to help explain both the conformational changes and the different denaturation behaviour of the genetic variants. RESULTS We have redetermined the structure of beta-Lg lattice Z at 3.0 A resolution by multiple isomorphous replacement and have partially refined it (R factor = 24.8%). Using the dimer from this lattice Z structure as a search model, the triclinic crystal form grown at pH 6.5 (lattice X) has been solved by molecular replacement. Refinement of lattice X at 1.8 A resolution gave an R factor of 18.1%. The structure we have determined differs from previously published structures in several ways. CONCLUSIONS Incorrect threading of the sequence in the published structures of beta-Lg affects four of the nine beta strands. The basic lipocalin fold of the polypeptide chain is unchanged, however. The relative orientation of the monomers in the beta-Lg dimer differs in the two lattices. On raising the pH, there is a rotation of approximately 5 degrees, which breaks a number of intersubunit hydrogen bonds. It is not yet clear, however, why the stability of the structure should depend so heavily upon the external loop around residue 64 or the beta strand with the free thiol, each of which shows genetic variation.
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Affiliation(s)
- S Brownlow
- Leeds Centre for Molecular Recognition in Biological Systems, Department of Biochemistry and Molecular Biology, The University of Leeds, Leeds, LS2 9JT, UK
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