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Bokhove M, Kawamura T, Okumura H, Goto S, Kawano Y, Werner S, Jarczowski F, Klimyuk V, Saito A, Kumasaka T. The structure of the rat vitamin B 12 transporter TC and its complex with glutathionylcobalamin. J Biol Chem 2024; 300:107289. [PMID: 38636663 PMCID: PMC11107200 DOI: 10.1016/j.jbc.2024.107289] [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: 12/21/2023] [Revised: 04/07/2024] [Accepted: 04/09/2024] [Indexed: 04/20/2024] Open
Abstract
Vitamin B12 (cobalamin or Cbl) functions as a cofactor in two important enzymatic processes in human cells, and life is not sustainable without it. B12 is obtained from food and travels from the stomach, through the intestine, and into the bloodstream by three B12-transporting proteins: salivary haptocorrin (HC), gastric intrinsic factor, and transcobalamin (TC), which all bind B12 with high affinity and require proteolytic degradation to liberate Cbl. After intracellular delivery of dietary B12, Cbl in the aquo/hydroxocobalamin form can coordinate various nucleophiles, for example, GSH, giving rise to glutathionylcobalamin (GSCbl), a naturally occurring form of vitamin B12. Currently, there is no data showing whether GSCbl is recognized and transported in the human body. Our crystallographic data shows for the first time the complex between a vitamin B12 transporter and GSCbl, which compared to aquo/hydroxocobalamin, binds TC equally well. Furthermore, sequence analysis and structural comparisons show that TC recognizes and transports GSCbl and that the residues involved are conserved among TCs from different organisms. Interestingly, haptocorrin and intrinsic factor are not structurally tailored to bind GSCbl. This study provides new insights into the interactions between TC and Cbl.
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Affiliation(s)
- Marcel Bokhove
- Structural Biology Division, Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo, Japan.
| | - Takashi Kawamura
- Structural Biology Division, Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo, Japan
| | - Hideo Okumura
- Structural Biology Division, Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo, Japan
| | - Sawako Goto
- Department of Applied Molecular Medicine, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, Japan
| | - Yoshiaki Kawano
- Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo, Hyogo, Japan
| | | | | | | | - Akihiko Saito
- Department of Applied Molecular Medicine, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Chuo-ku, Niigata, Japan
| | - Takashi Kumasaka
- Structural Biology Division, Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo, Japan.
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2
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McCorvie TJ, Ferreira D, Yue WW, Froese DS. The complex machinery of human cobalamin metabolism. J Inherit Metab Dis 2023; 46:406-420. [PMID: 36680553 DOI: 10.1002/jimd.12593] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 01/17/2023] [Accepted: 01/19/2023] [Indexed: 01/22/2023]
Abstract
Vitamin B12 (cobalamin, Cbl) is required as a cofactor by two human enzymes, 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR) and methylmalonyl-CoA mutase (MMUT). Within the body, a vast array of transporters, enzymes and chaperones are required for the generation and delivery of these cofactor forms. How they perform these functions is dictated by the structure and interactions of the proteins involved, the molecular bases of which are only now being elucidated. In this review, we highlight recent insights into human Cbl metabolism and address open questions in the field by employing a protein structure and interactome based perspective. We discuss how three very similar proteins-haptocorrin, intrinsic factor and transcobalamin-exploit slight structural differences and unique ligand receptor interactions to effect selective Cbl absorption and internalisation. We describe recent advances in the understanding of how endocytosed Cbl is transported across the lysosomal membrane and the implications of the recently solved ABCD4 structure. We detail how MMACHC and MMADHC cooperate to modify and target cytosolic Cbl to the client enzymes MTR and MMUT using ingenious modifications to an ancient nitroreductase fold, and how MTR and MMUT link with their accessory enzymes to sustainably harness the supernucleophilic potential of Cbl. Finally, we provide an outlook on how future studies may combine structural and interactome based approaches and incorporate knowledge of post-translational modifications to bring further insights.
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Affiliation(s)
- Thomas J McCorvie
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Douglas Ferreira
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, UK
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Wyatt W Yue
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - D Sean Froese
- Division of Metabolism and Children's Research Center, University Children's Hospital Zürich, University of Zürich, Zürich, Switzerland
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3
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Temova Rakuša Ž, Roškar R, Hickey N, Geremia S. Vitamin B 12 in Foods, Food Supplements, and Medicines-A Review of Its Role and Properties with a Focus on Its Stability. MOLECULES (BASEL, SWITZERLAND) 2022; 28:molecules28010240. [PMID: 36615431 PMCID: PMC9822362 DOI: 10.3390/molecules28010240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 12/21/2022] [Accepted: 12/22/2022] [Indexed: 12/29/2022]
Abstract
Vitamin B12, also known as the anti-pernicious anemia factor, is an essential micronutrient totally dependent on dietary sources that is commonly integrated with food supplements. Four vitamin B12 forms-cyanocobalamin, hydroxocobalamin, 5'-deoxyadenosylcobalamin, and methylcobalamin-are currently used for supplementation and, here, we provide an overview of their biochemical role, bioavailability, and efficacy in different dosage forms. Since the effective quantity of vitamin B12 depends on the stability of the different forms, we further provide a review of their main reactivity and stability under exposure to various environmental factors (e.g., temperature, pH, light) and the presence of some typical interacting compounds (oxidants, reductants, and other water-soluble vitamins). Further, we explore how the manufacturing process and storage affect B12 stability in foods, food supplements, and medicines and provide a summary of the data published to date on the content-related quality of vitamin B12 products on the market. We also provide an overview of the approaches toward their stabilization, including minimization of the destabilizing factors, addition of proper stabilizers, or application of some (innovative) technological processes that could be implemented and contribute to the production of high-quality vitamin B12 products.
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Affiliation(s)
| | - Robert Roškar
- Faculty of Pharmacy, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Neal Hickey
- Department of Chemical and Pharmaceutical Sciences, Centre of Excellence in Biocrystallography, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
| | - Silvano Geremia
- Department of Chemical and Pharmaceutical Sciences, Centre of Excellence in Biocrystallography, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
- Correspondence:
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4
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Nijland M, Martínez Felices JM, Slotboom DJ, Thangaratnarajah C. Membrane transport of cobalamin. VITAMINS AND HORMONES 2022; 119:121-148. [PMID: 35337617 DOI: 10.1016/bs.vh.2022.01.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A wide variety of organisms encode cobalamin-dependent enzymes catalyzing essential metabolic reactions, but the cofactor cobalamin (vitamin B12) is only synthesized by a subset of bacteria and archaea. The biosynthesis of cobalamin is complex and energetically costly, making cobalamin variants and precursors metabolically valuable. Auxotrophs for these molecules have evolved uptake mechanisms to compensate for the lack of a synthesis pathway. Bacterial transport of cobalamin involves the passage over one or two lipidic membranes in Gram-positive and -negative bacteria, respectively. In higher eukaryotes, a complex system of carriers, receptors and transporters facilitates the delivery of the essential molecule to the tissues. Biochemical and genetic approaches have identified different transporter families involved in cobalamin transport. The majority of the characterized cobalamin transporters are active transport systems that belong to the ATP-binding cassette (ABC) superfamily of transporters. In this chapter, we describe the different cobalamin transport systems characterized to date that are present in bacteria and humans, as well as yet-to-be-identified transporters.
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Affiliation(s)
- Mark Nijland
- University of Groningen, Faculty of Science and Engineering, Groningen Biomolecular Sciences and Biotechnology, Membrane Enzymology Group, Groningen, Netherlands
| | - Jose M Martínez Felices
- University of Groningen, Faculty of Science and Engineering, Groningen Biomolecular Sciences and Biotechnology, Membrane Enzymology Group, Groningen, Netherlands
| | - Dirk J Slotboom
- University of Groningen, Faculty of Science and Engineering, Groningen Biomolecular Sciences and Biotechnology, Membrane Enzymology Group, Groningen, Netherlands.
| | - Chancievan Thangaratnarajah
- University of Groningen, Faculty of Science and Engineering, Groningen Biomolecular Sciences and Biotechnology, Membrane Enzymology Group, Groningen, Netherlands
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5
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Federizon J, Feugmo CGT, Huang WC, He X, Miura K, Razi A, Ortega J, Karttunen M, Lovell JF. Experimental and Computational Observations of Immunogenic Cobalt Porphyrin Lipid Bilayers: Nanodomain-Enhanced Antigen Association. Pharmaceutics 2021; 13:pharmaceutics13010098. [PMID: 33466686 PMCID: PMC7828809 DOI: 10.3390/pharmaceutics13010098] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Revised: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 12/18/2022] Open
Abstract
Cobalt porphyrin phospholipid (CoPoP) can incorporate within bilayers to enable non-covalent surface-display of antigens on liposomes by mixing with proteins bearing a polyhistidine tag (his-tag); however, the mechanisms for how this occurs are poorly understood. These were investigated using the his-tagged model antigen Pfs25, a protein antigen candidate for malaria transmission-blocking vaccines. Pfs25 was found to associate with the small molecule aquocobalamin, a form of vitamin B12 and a cobalt-containing corrin macrocycle, but without particle formation, enabling comparative assessment. Relative to CoPoP liposomes, binding and serum stability studies indicated a weaker association of Pfs25 to aquocobalamin or cobalt nitrilotriacetic acid (Co-NTA) liposomes, which have cobalt displayed in the aqueous phase on lipid headgroups. Antigen internalization by macrophages was enhanced with Pfs25 bound to CoPoP liposomes. Immunization in mice with Pfs25 bound to CoPoP liposomes elicited antibodies that recognized ookinetes and showed transmission-reducing activity. To explore the physical mechanisms involved, we employed molecular dynamics (MD) simulations of bilayers containing phospholipid, cholesterol, as well as either CoPoP or NTA-functionalized lipids. The results show that the CoPoP-containing bilayer creates nanodomains that allow access for a limited but sufficient amount of water molecules that could be replaced by his-tags due to their favorable free energy properties allowing for stabilization. The position of the metal center within the NTA liposomes was much more exposed to the aqueous environment, which could explain its limited capacity for stabilizing Pfs25. This study illustrates the impact of CoPoP-induced antigen particleization in enhancing vaccine efficacy, and provides molecular insights into the CoPoP bilayer properties that enable this.
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Affiliation(s)
- Jasmin Federizon
- Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260, USA; (J.F.); (W.-C.H.); (X.H.)
| | | | - Wei-Chiao Huang
- Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260, USA; (J.F.); (W.-C.H.); (X.H.)
| | - Xuedan He
- Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260, USA; (J.F.); (W.-C.H.); (X.H.)
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA;
| | - Aida Razi
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada; (A.R.); (J.O.)
| | - Joaquin Ortega
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada; (A.R.); (J.O.)
| | - Mikko Karttunen
- Department of Chemistry, the University of Western Ontario, London, ON N6A 3K7, Canada;
- Centre for Advanced Materials and Biomaterials Research, the University of Western Ontario, London, ON N6A 3K7, Canada
- Department of Applied Mathematics, the University of Western Ontario, London, ON N6A 5B7, Canada
- Correspondence: (M.K.); (J.F.L.)
| | - Jonathan F. Lovell
- Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260, USA; (J.F.); (W.-C.H.); (X.H.)
- Correspondence: (M.K.); (J.F.L.)
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The Origins of Salivary Vitamin A, Vitamin B 12 and Vitamin D-Binding Proteins. Nutrients 2020; 12:nu12123838. [PMID: 33339130 PMCID: PMC7765569 DOI: 10.3390/nu12123838] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 11/16/2022] Open
Abstract
Vitamin A- (retinol), vitamin B12- (haptocorrin) and vitamin D-binding proteins are the major circulatory transporters of their respective ligands; they are also constituents of the salivary proteome, the origins of which, remain unclear. The aim of this study was to explore how these proteins enter saliva and their relationship (if any) with vitamin status. Firstly, the three vitamin-binding proteins were quantified in resting whole mouth saliva and chewing-stimulated saliva from healthy donors (n = 10) to determine if they enter the mouth by salivary secretion or from the circulation. Secondly paired whole mouth saliva and serum samples were analysed from healthy donors (n = 14) to determine the relationships between the vitamin-binding proteins and vitamin status. Salivary output of all three vitamin-binding proteins studied increased when secretion was stimulated, suggesting they are secreted by the salivary glands. Whilst retinol-binding protein and haptocorrin were secreted by all major salivary glands, vitamin D-binding protein was restricted to the mucus glands. Salivary vitamin-binding protein concentrations were not found to be indicative of systemic vitamin status.
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Hinkel J, Schmitt J, Wurm M, Rosenbaum-Fabian S, Schwab KO, Jacobsen DW, Spiekerkoetter U, Fedosov SN, Hannibal L, Grünert SC. Elevated Plasma Vitamin B 12 in Patients with Hepatic Glycogen Storage Diseases. J Clin Med 2020; 9:jcm9082326. [PMID: 32707782 PMCID: PMC7463656 DOI: 10.3390/jcm9082326] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 07/13/2020] [Accepted: 07/17/2020] [Indexed: 12/14/2022] Open
Abstract
Background: Hepatic glycogen storage diseases (GSDs) are inborn errors of metabolism affecting the synthesis or breakdown of glycogen in the liver. This study, for the first time, systematically assessed vitamin B12 status in a large cohort of hepatic GSD patients. Methods: Plasma vitamin B12, total plasma homocysteine (tHcy) and methylmalonic acid concentrations were measured in 44 patients with hepatic GSDs and compared to 42 healthy age- and gender-matched controls. Correlations of vitamin B12 status with different disease markers of GSDs (including liver transaminase activities and triglycerides) as well as the vitamin B12 intake were studied. Results: GSD patients had significantly higher plasma vitamin B12 concentrations than healthy controls (p = 0.0002). Plasma vitamin B12 concentration remained elevated in GSD patients irrespective of vitamin B12 intake. Plasma vitamin B12 concentrations correlated negatively with triglyceride levels, whereas no correlations were detected with liver transaminase activities (GOT and GPT) in GSD patients. Merging biomarker data of healthy controls and GSD patients showed a positive correlation between vitamin B12 status and liver function, which suggests complex biomarker associations. A combined analysis of biomarkers permitted a reliable clustering of healthy controls versus GSD patients. Conclusions: Elevated plasma concentration of vitamin B12 (irrespective of B12 intake) is a common finding in patients with hepatic GSD. The negative correlation of plasma vitamin B12 with triglyceride levels suggests an influence of metabolic control on the vitamin B12 status of GSD patients. Elevated vitamin B12 was not correlated with GOT and GPT in our cohort of GSD patients. Merging of data from healthy controls and GSD patients yielded positive correlations between these biomarkers. This apparent dichotomy highlights the intrinsic complexity of biomarker associations and argues against generalizations of liver disease and elevated vitamin B12 in blood. Further studies are needed to determine whether the identified associations are causal or coincidental, and the possible impact of chronically elevated vitamin B12 on GSD.
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Affiliation(s)
- Julia Hinkel
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Johannes Schmitt
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Michael Wurm
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
- Department of Pediatrics, St. Hedwigs Campus, University Children’s Hospital Regensburg, 93049 Regensburg, Germany;
| | - Stefanie Rosenbaum-Fabian
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Karl Otfried Schwab
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Donald W. Jacobsen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA;
| | - Ute Spiekerkoetter
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Sergey N. Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark;
| | - Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Center - University of Freiburg, Faculty of Medicine, 79106 Freiburg, Germany
- Correspondence: (L.H.); (S.C.G.)
| | - Sarah C. Grünert
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
- Correspondence: (L.H.); (S.C.G.)
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8
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Frawley KL, Carpenter Totoni S, Bae Y, Pearce LL, Peterson J. A Comparison of Potential Azide Antidotes in a Mouse Model. Chem Res Toxicol 2020; 33:594-603. [PMID: 31922405 DOI: 10.1021/acs.chemrestox.9b00422] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Three cobalt-containing macrocyclic compounds previously shown to antagonize cyanide toxicity have been comparatively evaluated for the amelioration of sublethal azide toxicity in juvenile (7-8 weeks) Swiss-Webster mice. The lowest effective doses were determined for hydroxocobalamin, a cobalt porphyrin, and a cobalt-Schiff base macrocycle by giving the antidotes 5 min prior to the toxicant, 27 mg (415 μmol) /kg sodium azide. Both male and female mice were evaluated for their response to the toxicant as well as the antidotes, and no significant differences were noted once weight differences were taken into account. Two of the three compounds significantly decreased the recovery time of azide-intoxicated mice at 10 min after the administration of sodium azide, as determined by a behavioral test (pole climbing). Additionally, azide was determined to cause a several degree drop (∼3 °C) in measured tail temperature, and warming the mice led to a more rapid recovery. The mice were also shown to recover more rapidly when given sodium nitrite, 24 mg (350 μmol)/kg, 5 min after the toxicant; this treatment also suppressed the azide-induced tail temperature decrease. Electron paramagnetic resonance (EPR) measurements of mouse blood treated with sodium azide demonstrated the presence of nitrosylhemoglobin at levels of 10-20 μM which persisted for ∼300 min. The presence of the methemoglobin azide adduct was also detected by EPR at a maximum level of ∼300 μM, but these signals disappeared around 200 min after the administration of azide. The treatment of mice with 15N sodium azide proved that the nitrosylhemoglobin was a product of the administered azide by the appearance of a two-line hyperfine (due to the 15N) in the EPR spectrum of mouse blood.
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Affiliation(s)
- Kristin L Frawley
- Department of Environmental and Occupational Health, Graduate School of Public Health , The University of Pittsburgh , 130 DeSoto Street , Pittsburgh , Pennsylvania 15219 , United States
| | - Samantha Carpenter Totoni
- Department of Environmental and Occupational Health, Graduate School of Public Health , The University of Pittsburgh , 130 DeSoto Street , Pittsburgh , Pennsylvania 15219 , United States
| | - Yookyung Bae
- Department of Environmental and Occupational Health, Graduate School of Public Health , The University of Pittsburgh , 130 DeSoto Street , Pittsburgh , Pennsylvania 15219 , United States
| | - Linda L Pearce
- Department of Environmental and Occupational Health, Graduate School of Public Health , The University of Pittsburgh , 130 DeSoto Street , Pittsburgh , Pennsylvania 15219 , United States
| | - Jim Peterson
- Department of Environmental and Occupational Health, Graduate School of Public Health , The University of Pittsburgh , 130 DeSoto Street , Pittsburgh , Pennsylvania 15219 , United States
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Determination of free cyano-cobinamide in swine and rabbit plasma by liquid chromatography tandem mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2019; 1124:100-108. [PMID: 31185415 DOI: 10.1016/j.jchromb.2019.05.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 05/16/2019] [Accepted: 05/18/2019] [Indexed: 11/20/2022]
Abstract
In recent years, Cobinamide (Cbi) has shown promise as a therapeutic for cyanide poisoning. There are several forms of Cbi based on the identity of the ligands bound to the cobalt in Cbi and these different forms of Cbi have divergent behavior (e.g., the aquo and hydroxo forms of Cbi readily bind to proteins, limiting their distribution significantly, whereas [Cbi(CN)2] does not). While current analysis techniques only measure total Cbi, methods to elucidate the behavior of 'available' Cbi versus cyanide-complexed Cbi would be valuable for biomedical and pharmacokinetic studies. Therefore, a method was developed for the analysis of cyanide-complexed Cbi in plasma via liquid chromatography tandem mass spectrometry (LC-MS-MS). Plasma samples were prepared by denaturing proteins with 10% ammonium hydroxide in acetonitrile. The resulting mixture was centrifuged, and the supernatant was removed, dried, and reconstituted. Cyanide-complexed Cbi was then analyzed via LC-MS-MS. The limit of detection was 0.2 μM, and the linear dynamic range was between 1 and 200 μM. The accuracy was 100 ± 17% and the precision, measured by relative standard deviation (%RSD), was ≤18.5%. Carryover, a severe problem when analyzing Cbi via liquid chromatography was eliminated using a polymeric-based stationary phase (PLRP-S) and a controlled washing protocol. The method allowed evaluation of the cyanide-bound and 'available' Cbi from treated animals and, when paired with a method for total Cbi analysis, allows for estimation of Cbi utilization when treating cyanide poisoning.
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10
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Fedosov SN, Nexo E, Heegaard CW. Vitamin B 12 and its binding proteins in milk from cow and buffalo in relation to bioavailability of B 12. J Dairy Sci 2019; 102:4891-4905. [PMID: 30928264 DOI: 10.3168/jds.2018-15016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 02/07/2019] [Indexed: 11/19/2022]
Abstract
Milk is an important source of highly bioavailable vitamin B12 (cobalamin) in human nutrition. In most animal products, vitamin B12 is strongly bound to various specific protein carriers. The 2 vitamin B12-specific proteins, predominantly transcobalamin (TC) and haptocorrin (HC), were earlier found in milk from Holstein Friesian cows and in human or sow milk, respectively. As the type of vitamin B12 binders may influence bioavailability of the vitamin, we examined vitamin B12 carriers in pooled milk specimens derived from European and Indian cow and buffalo herds. The total endogenous vitamin B12 concentration was comparable in all milk pools (≈3 nM), but the vitamin carriers varied considerably: TC + caseins in Danish cows, TC + HC in Indian cows and buffaloes, and mainly HC in Italian buffaloes. Danish cow milk contained half as much TC as vitamin B12, and the surplus vitamin was all attached via a single coordination bond to abundantly available histidine residues of casein. The specific binding proteins in Indian cow milk (TC + HC) approximately matched the molar content of vitamin B12. Milk from the 2 buffalo breeds contained more specific binders than vitamin B12, and the surplus proteins included the unsaturated TC ≈ 3 nM (Indian stock), or both TC ≈ 4 nM and HC ≈ 23 nM (Italian stock). The abundant HC of the latter sample bound nearly all endogenous vitamin B12. We tested (in vitro) the transfer of vitamin B12 from milk proteins to human carriers, involved in the intestinal uptake. The bovine TC-vitamin B12 complex rapidly dissociated at pH 2 (time of half reaction, τ1/2 < 1 min, 37°C) and was susceptible to digestion with trypsin + chymotrypsin (pH 7.5). Transfer of vitamin B12 from the precipitated bovine casein (pH 2) to human carriers proceeded with τ1/2 ≈ 7 min (37°C) and τ1/2 ≈ 35 min (20°C). Liberation of vitamin B12 from buffalo HC was hampered because of its pH stability and slow proteolysis. Nutritional availability of vitamin B12 is expected to be high in cow milk (with TC-vitamin B12 and casein-vitamin B12 complexes) but potentially constrained in buffalo milk (with HC-vitamin B12). This especially concerns the Italian buffalo milk, where a high excess of HC was found. We speculate whether the isolated stock of Italian buffalo maintained the ancestral secretion of carriers (HC ≫ vitamin B12, TC ≈ 0), whereas intensive crossbreeding of cows and buffaloes from other regions caused a change to TC ≤ vitamin B12, with low or absent HC. The substitution of HC by less sturdy carriers is apparently more beneficial to human consumers as far as vitamin B12 bioavailability is concerned.
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Affiliation(s)
- Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Science Park, Gustav Wieds Vej 10C 8000, Aarhus C, Denmark.
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, Science Park, Gustav Wieds Vej 10C 8000, Aarhus C, Denmark
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11
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Expression of TCN1 in Blood is Negatively Associated with Verbal Declarative Memory Performance. Sci Rep 2018; 8:12654. [PMID: 30139959 PMCID: PMC6107676 DOI: 10.1038/s41598-018-30898-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 08/01/2018] [Indexed: 12/29/2022] Open
Abstract
Memory is indispensable for normal cognitive functioning, and the ability to store and retrieve information is central to mental health and disease. The molecular mechanisms underlying complex memory functions are largely unknown, but multiple genome-wide association studies suggest that gene regulation may play a role in memory dysfunction. We performed a global gene expression analysis using a large and balanced case-control sample (n = 754) consisting of healthy controls and schizophrenia and bipolar disorder patients. Our aim was to discover genes that are differentially expressed in relation to memory performance. Gene expression in blood was measured using Illumina HumanHT-12 v4 Expression BeadChip and memory performance was assessed with the updated California Verbal Learning Test (CVLT-II). We found that elevated expression of the vitamin B12-related gene TCN1 (haptocorrin) was significantly associated with poorer memory performance after correcting for multiple testing (β = −1.50, p = 3.75e-08). This finding was validated by quantitative real-time PCR and followed up with additional analyses adjusting for confounding variables. We also attempted to replicate the finding in an independent case-control sample (n = 578). The relationship between TCN1 expression and memory impairment was comparable to that of important determinants of memory function such as age and sex, suggesting that TCN1 could be a clinically relevant marker of memory performance. Thus, we identify TCN1 as a novel genetic finding associated with poor memory function. This finding may have important implications for the diagnosis and treatment of vitamin B12-related conditions.
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Dereven'kov IA, Hannibal L, Makarov SV, Makarova AS, Molodtsov PA, Koifman OI. Characterization of the complex between native and reduced bovine serum albumin with aquacobalamin and evidence of dual tetrapyrrole binding. J Biol Inorg Chem 2018; 23:725-738. [PMID: 29721769 DOI: 10.1007/s00775-018-1562-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Accepted: 04/25/2018] [Indexed: 11/30/2022]
Abstract
Serum albumin binds to a variety of endogenous ligands and drugs. Human serum albumin (HSA) binds to heme via hydrophobic interactions and axial coordination of the iron center by protein residue Tyr161. Human serum albumin binds to another tetrapyrrole, cobalamin (Cbl), but the structural and functional properties of this complex are poorly understood. Herein, we investigate the reaction between aquacobalamin (H2OCbl) and bovine serum albumin (BSA, the bovine counterpart of HSA) using Ultraviolet-Visible and fluorescent spectroscopy, and electron paramagnetic resonance. The reaction between H2OCbl and BSA led to the formation of a BSA-Cbl(III) complex consistent with N-axial ligation (amino). Prior to the formation of this complex, the reactants participate in an additional binding event that has been examined by fluorescence spectroscopy. Binding of BSA to Cbl(III) reduced complex formation between the bound cobalamin and free cyanide to form cyanocobalamin (CNCbl), suggesting that the β-axial position of the cobalamin may be occupied by an amino acid residue from the protein. Reaction of BSA containing reduced disulfide bonds with H2OCbl produces cob(II)alamin and disulfide with intermediate formation of thiolate Cbl(III)-BSA complex and its decomposition. Finally, in vitro studies showed that cobalamin binds to BSA only in the presence of an excess of protein, which is in contrast to heme binding to BSA that involves a 1:1 stoichiometry. In vitro formation of BSA-Cbl(III) complex does not preclude subsequent heme binding, which occurs without displacement of H2OCbl bound to BSA. These data suggest that the two tetrapyrroles interact with BSA in different binding pockets.
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Affiliation(s)
- Ilia A Dereven'kov
- Institute of Macroheterocyclic Compounds, Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, Ivanovo, 153000, Russian Federation.
| | - Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg, Mathildenstr. 1, 79106, Freiburg, Germany
| | - Sergei V Makarov
- Institute of Macroheterocyclic Compounds, Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, Ivanovo, 153000, Russian Federation
| | - Anna S Makarova
- G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Academicheskaya Str 1, Ivanovo, 153045, Russian Federation
| | - Pavel A Molodtsov
- Institute of Macroheterocyclic Compounds, Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, Ivanovo, 153000, Russian Federation
| | - Oskar I Koifman
- Institute of Macroheterocyclic Compounds, Ivanovo State University of Chemistry and Technology, Sheremetevskiy Str. 7, Ivanovo, 153000, Russian Federation
- G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Academicheskaya Str 1, Ivanovo, 153045, Russian Federation
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Mutti E, Hunger M, Fedosov S, Nexo E, Kräutler B. Organometallic DNA-B 12 Conjugates as Potential Oligonucleotide Vectors: Synthesis and Structural and Binding Studies with Human Cobalamin-Transport Proteins. Chembiochem 2017; 18:2280-2291. [PMID: 28881087 DOI: 10.1002/cbic.201700472] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Indexed: 12/14/2022]
Abstract
The synthesis and structural characterization of Co-(dN)25 -Cbl (Cbl: cobalamin; dN: deoxynucleotide) and Co-(dN)39 -Cbl, which are organometallic DNA-B12 conjugates with single DNA strands consisting of 25 and 39 deoxynucleotides, respectively, and binding studies of these two DNA-Cbl conjugates to three homologous human Cbl transporting proteins, transcobalamin (TC), intrinsic factor (IF), and haptocorrin (HC), are reported. This investigation tests the suitability of such DNA-Cbls for the task of eventual in vivo oligonucleotide delivery. The binding of DNA-Cbl to TC, IF, and HC was investigated in competition with either a fluorescent Cbl derivative and Co-(dN)25 -Cbl, or radiolabeled vitamin B12 (57 Co-CNCbl) and Co-(dN)25 -Cbl or Co-(dN)39 -Cbl. Binding of the new DNA-Cbl conjugates was fast and tight with TC, but poorer with HC and IF, which extends a similar original finding with the simpler DNA-Cbl, Co-(dN)18 -Cbl. The contrasting affinities of TC versus IF and HC for the DNA-Cbl conjugates are rationalized herein by a stepwise mechanism of Cbl binding. Critical contributions to overall affinity result from gradual conformational adaptations of the Cbl-binding proteins to the DNA-Cbl, which is first bound to the respective β domains. This transition is fast with TC, but slow with IF and HC, with which weaker binding results. The invariably tight interaction of the DNA-Cbl conjugates with TC makes the Cbl moiety a potential natural vector for the specific delivery of oligonucleotide loads from the blood into cells.
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Affiliation(s)
- Elena Mutti
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Miriam Hunger
- Institute of Organic Chemistry, Center for Molecular Biosciences (CMBI), University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria
| | - Sergey Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Science Park Gustav WiedsVej 10C, 8000, Aarhus C, Denmark
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Bernhard Kräutler
- Institute of Organic Chemistry, Center for Molecular Biosciences (CMBI), University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria
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Structure of the human transcobalamin beta domain in four distinct states. PLoS One 2017; 12:e0184932. [PMID: 28910388 PMCID: PMC5599065 DOI: 10.1371/journal.pone.0184932] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 09/02/2017] [Indexed: 11/19/2022] Open
Abstract
Vitamin B12 (cyanocobalamin, CNCbl) is an essential cofactor-precursor for two biochemical reactions in humans. When ingested, cobalamins (Cbl) are transported via a multistep transport system into the bloodstream, where the soluble protein transcobalamin (TC) binds Cbl and the complex is taken up into the cells via receptor mediated endocytosis. Crystal structures of TC in complex with CNCbl have been solved previously. However, the initial steps of holo-TC assembly have remained elusive. Here, we present four crystal structures of the beta domain of human TC (TC-beta) in different substrate-bound states. These include the apo and CNCbl-bound states, providing insight into the early steps of holo-TC assembly. We found that in vitro assembly of TC-alpha and TC-beta to a complex was Cbl-dependent. We also determined the structure of TC-beta in complex with cobinamide (Cbi), an alternative substrate, shedding light on the specificity of TC. We finally determined the structure of TC-beta in complex with an inhibitory antivitamin B12 (anti-B12). We used this structure to model the binding of anti-B12 into full-length holo-TC and could rule out that the inhibitory function of anti-B12 was based on an inability to form a functional complex with TC.
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15
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Broderick KE, Potluri P, Zhuang S, Scheffler IE, Sharma VS, Pilz RB, Boss GR. Cyanide Detoxification by the Cobalamin Precursor Cobinamide. Exp Biol Med (Maywood) 2016; 231:641-9. [PMID: 16636313 DOI: 10.1177/153537020623100519] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Cyanide is a highly toxic agent that inhibits mitochondrial cytochrome-c oxidase, thereby depleting cellular ATP. it contributes to smoke inhalation deaths in fires and could be used as a weapon of mass destruction. Cobalamin (vitamin B12) binds cyanide with a relatively high affinity and is used in Europe to treat smoke inhalation victims. Cobinamide, the penultimate compound in cobalamin biosynthesis, binds cyanide with about 1010 greater affinity than cobalamin, and we found It was several-fold more effective than cobalamin in (i) reversing cyanide inhibition of oxidative phosphorylation in mammalian cells; (ii) rescuing mammalian cells and Drosophila melanogaster from cyanide toxicity; and (iii) reducing cyanide inhibition of Drosophila Malpighian tubule secretion. Cobinamide could be delivered by oral ingestion, inhalation, or injection to Drosophila, and it was as effective when administered up to 5 mins post-cyanide exposure as when given preexposure. We conclude that cobinamide is an effective cyanide detoxifying agent that has potential use as a cyanide antidote, both in smoke inhalation victims and in persons exposed to cyanide used as a weapon of mass destruction.
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Affiliation(s)
- Kate E Broderick
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0652, USA
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Nitrosyl-Cobinamide, a New and Direct Nitric Oxide–Releasing Drug Effective In Vivo. Exp Biol Med (Maywood) 2016; 232:1432-40. [DOI: 10.3181/0703-rm-70] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
A limited number of nitric oxide (NO)-generating drugs are available for clinical use for acute and chronic conditions. Most of these agents are organic nitrates, which do not directly release NO; tolerance to the drugs develops, in part, as a consequence of their conversion to NO. We synthesized nitrosyl-cobinamide (NO-Cbi) from cobinamide, a structural analog of cobalamin (vitamin B12). NO-Cbi is a direct NO-releasing agent that we found was stable in water, but under physiologic conditions, it released NO with a half-life of 30 mins to 1 h. We show in five different biological systems that NO-Cbi is an effective NO-releasing drug. First, in cultured rat vascular smooth muscle cells, NO-Cbi induced phosphorylation of vasodilator-stimulated phosphoprotein, a downstream target of cGMP and cGMP-dependent protein kinase. Second, in isolated Drosophila melanogaster Malpighian tubules, NO-Cbi–stimulated fluid secretion was similar to that stimulated by Deta-NONOate and a cGMP analog. Third, in isolated mouse hearts, NO-Cbi increased coronary flow much more potently than nitroglycerin. Fourth, in contracted mouse aortic rings, NO-Cbi induced relaxation, albeit to a lesser extent than sodium nitroprusside. Fifth, in intact mice, a single NO-Cbi injection rapidly reduced blood pressure, and blood pressure returned to normal after 45 mins; repeated NO-Cbi injections induced the expected fall in blood pressure. These studies indicate that NO-Cbi is a useful NO donor that can be used experimentally in the laboratory; moreover, it could be developed into a vasodilating drug for treating hypertension and potentially other diseases such as angina and congestive heart failure.
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17
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Obeid R, Fedosov SN, Nexo E. Cobalamin coenzyme forms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamin deficiency. Mol Nutr Food Res 2015; 59:1364-72. [PMID: 25820384 PMCID: PMC4692085 DOI: 10.1002/mnfr.201500019] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/25/2015] [Accepted: 03/25/2015] [Indexed: 12/12/2022]
Abstract
Methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl) are coenzymes for methionine synthase and methylmalonyl-CoA mutase, respectively. Hydroxylcobalamin (HOCbl) and cyanocobalamin (CNCbl) are frequently used for supplementation. MeCbl and AdoCbl have recently emerged as alternative forms in supplements. In the light of metabolic transformation of Cbl into its cofactor forms, this review discusses current evidence on efficacy and utility of different Cbl forms in preventing or treating Cbl deficiency. Cbl-transporting proteins bind and mediate the uptake of all aforementioned forms of Cbl. After internalization and lysosomal release, Cbl binds to the cytosolic chaperon MMACHC that is responsible for (i) flavin-dependent decyanation of [CN-Co3+]Cbl to [Co2+]Cbl; (ii) glutathione-dependent dealkylation of MeCbl and AdoCbl to [Co2+/1+]Cbl; and (iii) glutathione-dependent decyanation of CNCbl or reduction of HOCbl under anaerobic conditions. MMACHC shows a broad specificity for Cbl forms and supplies the Cbl2+ intermediate for synthesis of MeCbl and AdoCbl. Cobalamin chemistry, physiology, and biochemistry suggest that MeCbl and AdoCbl follow the same route of intracellular processing as CNCbl does. We conclude that supplementing MeCbl or AdoCbl is unlikely to be advantageous compared to CNCbl. On the other hand, there are obvious advantages of high parenteral doses (1–2 mg) of HOCbl in treating inborn errors of Cbl metabolism.
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Affiliation(s)
- Rima Obeid
- Aarhus Institute of Advanced Studies, , University of Aarhus, Aarhus, Denmark.,Department of Clinical Chemistry, University Hospital of the Saarland, Homburg, Germany
| | - Sergey N Fedosov
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus C, Denmark.,Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus C, Denmark
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18
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Butzin NC, Secinaro MA, Swithers KS, Gogarten JP, Noll KM. Thermotoga lettingae can salvage cobinamide to synthesize vitamin B12. Appl Environ Microbiol 2013; 79:7006-12. [PMID: 24014541 PMCID: PMC3811540 DOI: 10.1128/aem.01800-13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 09/01/2013] [Indexed: 01/20/2023] Open
Abstract
We recently reported that the Thermotogales acquired the ability to synthesize vitamin B12 by acquisition of genes from two distantly related lineages, Archaea and Firmicutes (K. S. Swithers et al., Genome Biol. Evol. 4:730-739, 2012). Ancestral state reconstruction suggested that the cobinamide salvage gene cluster was present in the Thermotogales' most recent common ancestor. We also predicted that Thermotoga lettingae could not synthesize B12 de novo but could use the cobinamide salvage pathway to synthesize B12. In this study, these hypotheses were tested, and we found that Tt. lettingae did not synthesize B12 de novo but salvaged cobinamide. The growth rate of Tt. lettingae increased with the addition of B12 or cobinamide to its medium. It synthesized B12 when the medium was supplemented with cobinamide, and no B12 was detected in cells grown on cobinamide-deficient medium. Upstream of the cobinamide salvage genes is a putative B12 riboswitch. In other organisms, B12 riboswitches allow for higher transcriptional activity in the absence of B12. When Tt. lettingae was grown with no B12, the salvage genes were upregulated compared to cells grown with B12 or cobinamide. Another gene cluster with a putative B12 riboswitch upstream is the btuFCD ABC transporter, and it showed a transcription pattern similar to that of the cobinamide salvage genes. The BtuF proteins from species that can and cannot salvage cobinamides were shown in vitro to bind both B12 and cobinamide. These results suggest that Thermotogales species can use the BtuFCD transporter to import both B12 and cobinamide, even if they cannot salvage cobinamide.
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Affiliation(s)
- Nicholas C Butzin
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
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19
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Quadros EV, Sequeira JM. Cellular uptake of cobalamin: transcobalamin and the TCblR/CD320 receptor. Biochimie 2013; 95:1008-18. [PMID: 23415653 PMCID: PMC3902480 DOI: 10.1016/j.biochi.2013.02.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2013] [Accepted: 02/01/2013] [Indexed: 02/06/2023]
Abstract
Cellular uptake of cobalamin is facilitated by a receptor-mediated endocytosis process involving transcobalamin, a plasma protein that binds cobalamin and a cell surface receptor that specifically binds transcobalamin saturated with cobalamin. Intracellular Cbl concentration is maintained by modulating the expression of the receptor, which is cell cycle associated with highest expression in actively proliferating cells and an efflux system that shunts the excess cobalamin out of the cells for mobilization to other tissues where it is most needed. This review describes the process, proteins involved and genes encoding these proteins.
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Affiliation(s)
- Edward V Quadros
- Departments of Medicine / Cell Biology, SUNY- Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
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Gherasim C, Lofgren M, Banerjee R. Navigating the B(12) road: assimilation, delivery, and disorders of cobalamin. J Biol Chem 2013; 288:13186-93. [PMID: 23539619 DOI: 10.1074/jbc.r113.458810] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The reactivity of the cobalt-carbon bond in cobalamins is the key to their chemical versatility, supporting both methyl transfer and isomerization reactions. During evolution of higher eukaryotes that utilize vitamin B12, the high reactivity of the cofactor coupled with its low abundance pressured development of an efficient system for uptake, assimilation, and delivery of the cofactor to client B12-dependent enzymes. Although most proteins suspected to be involved in B12 trafficking were discovered by 2009, the recent identification of a new protein reveals that the quest for elucidating the intracellular B12 highway is still far from complete. Herein, we review the biochemistry of cobalamin trafficking.
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Affiliation(s)
- Carmen Gherasim
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI 48109-0600, USA
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Greibe E, Fedosov S, Sorensen BS, Højrup P, Poulsen SS, Nexo E. A single rainbow trout cobalamin-binding protein stands in for three human binders. J Biol Chem 2012; 287:33917-25. [PMID: 22872637 DOI: 10.1074/jbc.m112.398016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cobalamin uptake and transport in mammals are mediated by three cobalamin-binding proteins: haptocorrin, intrinsic factor, and transcobalamin. The nature of cobalamin-binding proteins in lower vertebrates remains to be elucidated. The aim of this study was to characterize the cobalamin-binding proteins of the rainbow trout (Oncorhynchus mykiss) and to compare their properties with those of the three human cobalamin-binding proteins. High cobalamin-binding capacity was found in trout stomach (210 pmol/g), roe (400 pmol/g), roe fluid (390 nmol/liter), and plasma (2500 nmol/liter). In all cases, it appeared to be the same protein based on analysis of partial sequences and immunological responses. The trout cobalamin-binding protein was purified from roe fluid, sequenced, and further characterized. Like haptocorrin, the trout cobalamin-binding protein was stable at low pH and had a high binding affinity for the cobalamin analog cobinamide. Like haptocorrin and transcobalamin, the trout cobalamin-binding protein was present in plasma and recognized ligands with altered nucleotide moiety. Like intrinsic factors, the trout cobalamin-binding protein was present in the stomach and resisted degradation by trypsin and chymotrypsin. It also resembled intrinsic factor in the composition of conserved residues in the primary cobalamin-binding site in the C terminus. The trout cobalamin-binding protein was glycosylated and displayed spectral properties comparable with those of haptocorrin and intrinsic factor. In conclusion, only one soluble cobalamin-binding protein was identified in the rainbow trout, a protein that structurally behaves like an intermediate between the three human cobalamin-binding proteins.
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Affiliation(s)
- Eva Greibe
- Department of Clinical Biochemistry, Aarhus University Hospital, 8000 Aarhus, Denmark.
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Furger E, Fedosov SN, Launholt Lildballe D, Waibel R, Schibli R, Nexo E, Fischer E. Comparison of recombinant human haptocorrin expressed in human embryonic kidney cells and native haptocorrin. PLoS One 2012; 7:e37421. [PMID: 22662153 PMCID: PMC3360681 DOI: 10.1371/journal.pone.0037421] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/20/2012] [Indexed: 02/02/2023] Open
Abstract
Haptocorrin (HC) is a circulating corrinoid binding protein with unclear function. In contrast to transcobalamin, the other transport protein in blood, HC is heavily glycosylated and binds a variety of cobalamin (Cbl) analogues. HC is present not only in blood but also in various secretions like milk, tears and saliva. No recombinant form of HC has been described so far. We report the expression of recombinant human HC (rhHC) in human embryonic kidney cells. We purified the protein with a yield of 6 mg (90 nmol) per litre of cell culture supernatant. The isolated rhHC behaved as native HC concerning its spectral properties and ability to recognize both Cbl and its baseless analogue cobinamide. Similar to native HC isolated from blood, rhHC bound to the asialoglycoprotein receptor only after removal of terminal sialic acid residues by treatment with neuraminidase. Interestingly, rhHC, that compared to native HC contains four excessive amino acids (…LVPR) at the C-terminus, showed subtle changes in the binding kinetics of Cbl, cobinamide and the fluorescent Cbl conjugate CBC. The recombinant protein has properties very similar to native HC and although showing slightly different ligand binding kinetics, rhHC is valuable for further biochemical and structural studies.
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Affiliation(s)
- Evelyne Furger
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, Villigen, Switzerland
| | | | | | - Robert Waibel
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, Villigen, Switzerland
| | - Roger Schibli
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, Villigen, Switzerland
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
| | - Eliane Fischer
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, Villigen, Switzerland
- * E-mail:
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Greibe E, Fedosov S, Nexo E. The cobalamin-binding protein in zebrafish is an intermediate between the three cobalamin-binding proteins in human. PLoS One 2012; 7:e35660. [PMID: 22532867 PMCID: PMC3331988 DOI: 10.1371/journal.pone.0035660] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 03/20/2012] [Indexed: 12/30/2022] Open
Abstract
In humans, three soluble extracellular cobalamin-binding proteins; transcobalamin (TC), intrinsic factor (IF), and haptocorrin (HC), are involved in the uptake and transport of cobalamin. In this study, we investigate a cobalamin-binding protein from zebrafish (Danio rerio) and summarize current knowledge concerning the phylogenetic evolution of kindred proteins. We identified a cobalamin binding capacity in zebrafish protein extracts (8.2 pmol/fish) and ambient water (13.5 pmol/fish) associated with a single protein. The protein showed resistance toward degradation by trypsin and chymotrypsin (like human IF, but unlike human HC and TC). The cobalamin analogue, cobinamide, bound weaker to the zebrafish cobalamin binder than to human HC, but stronger than to human TC and IF. Affinity for another analogue, adenosyl-pseudo-cobalamin was low compared with human HC and TC, but high compared with human IF. The absorbance spectrum of the purified protein in complex with hydroxo-cobalamin resembled those of human HC and IF, but not TC. We searched available databases to further explore the phylogenies of the three cobalamin-binding proteins in higher vertebrates. Apparently, TC-like proteins are the oldest evolutionary derivatives followed by IF and HC (the latter being present only in reptiles and most but not all mammals). Our findings suggest that the only cobalamin-binding protein in zebrafish is an intermediate between the three human cobalamin binders. These findings support the hypothesis about a common ancestral gene for all cobalamin-binding proteins in higher vertebrates.
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Affiliation(s)
- Eva Greibe
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark.
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Silla Y, Chandamouli B, Maiti S, Sengupta S. A Single Nucleotide Polymorphism in Transcobalamin II (I5V) Induces Structural Changes in the Protein As Revealed by Molecular Modeling Studies. Biochemistry 2011; 50:1396-402. [DOI: 10.1021/bi101095g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yumnam Silla
- Institute of Genomics and Integrative Biology (CSIR), Mall Road, New Delhi, India
| | | | - Souvik Maiti
- Institute of Genomics and Integrative Biology (CSIR), Mall Road, New Delhi, India
- National Chemical Laboratory (CSIR), Dr. Homi Bhabha Road, Pune, India
| | - Shantanu Sengupta
- Institute of Genomics and Integrative Biology (CSIR), Mall Road, New Delhi, India
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Abstract
Vitamin B12 (cobalamin, Cbl) is an essential nutrient in human metabolism. Genetic diseases of vitamin B12 utilisation constitute an important fraction of inherited newborn disease. Functionally, B12 is the cofactor for methionine synthase and methylmalonyl CoA mutase. To function as a cofactor, B12 must be metabolised through a complex pathway that modifies its structure and takes it through subcellular compartments of the cell. Through the study of inherited disorders of vitamin B12 utilisation, the genes for eight complementation groups have been identified, leading to the determination of the general structure of vitamin B12 processing and providing methods for carrier testing, prenatal diagnosis and approaches to treatment.
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Randaccio L, Geremia S, Demitri N, Wuerges J. Vitamin B12: unique metalorganic compounds and the most complex vitamins. Molecules 2010; 15:3228-59. [PMID: 20657474 PMCID: PMC6257451 DOI: 10.3390/molecules15053228] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 04/27/2010] [Accepted: 04/28/2010] [Indexed: 11/16/2022] Open
Abstract
The chemistry and biochemistry of the vitamin B(12) compounds (cobalamins, XCbl) are described, with particular emphasis on their structural aspects and their relationships with properties and function. A brief history of B(12), reveals how much the effort of chemists, biochemists and crystallographers have contributed in the past to understand the basic properties of this very complex vitamin. The properties of the two cobalamins, the two important B(12) cofactors Ado- and MeCbl are described, with particular emphasis on how the Co-C bond cleavage is involved in the enzymatic mechanisms. The main structural features of cobalamins are described, with particular reference to the axial fragment. The structure/property relationships in cobalamins are summarized. The recent studies on base-off/base-on equilibrium are emphasized for their relevance to the mode of binding of the cofactor to the protein scaffold. The absorption, transport and cellular uptake of cobalamins and the structure of the B(12) transport proteins, IF and TC, in mammals are reviewed. The B(12) transport in bacteria and the structure of the so far determined proteins are briefly described. The currently accepted mechanisms for the catalytic cycles of the AdoCbl and MeCbl enzymes are reported. The structure and function of B(12) enzymes, particularly the important mammalian enzymes methyltransferase (MetH) and methyl-malonyl-coenzyme A mutase (MMCM), are described and briefly discussed. Since fast proliferating cells require higher amount of vitamin B(12) than that required by normal cells, the study of B(12 )conjugates as targeting agents has recently gained importance. Bioconjugates have been studied as potential agents for delivering radioisotopes and NMR probes or as various cytotoxic agents towards cancer cells in humans and the most recent studies are described. Specifically, functionalized bioconjugates are used as "Trojan horses" to carry into the cell the appropriate antitumour or diagnostic label. Possible future developments of B(12) work are summarized.
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Affiliation(s)
- Lucio Randaccio
- Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy.
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Uhlich NA, Natalello A, Kadam RU, Doglia SM, Reymond JL, Darbre T. Structure and Binding of Peptide-Dendrimer Ligands to Vitamin B12. Chembiochem 2010; 11:358-65. [DOI: 10.1002/cbic.200900657] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Allis DG, Fairchild TJ, Doyle RP. The binding of vitamin B12 to transcobalamin(II); structural considerations for bioconjugate design—a molecular dynamics study. MOLECULAR BIOSYSTEMS 2010; 6:1611-8. [DOI: 10.1039/c003476b] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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A G-protein editor gates coenzyme B12 loading and is corrupted in methylmalonic aciduria. Proc Natl Acad Sci U S A 2009; 106:21567-72. [PMID: 19955418 DOI: 10.1073/pnas.0908106106] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mechanism by which docking fidelity is achieved for the multitude of cofactor-dependent enzymes is poorly understood. In this study, we demonstrate that delivery of coenzyme B(12) or 5'-deoxyadenosylcobalamin by adenosyltransferase to methylmalonyl-CoA mutase is gated by a small G protein, MeaB. While the GTP-binding energy is needed for the editing function; that is, to discriminate between active and inactive cofactor forms, the chemical energy of GTP hydrolysis is required for gating cofactor transfer. The G protein chaperone also exerts its editing function during turnover by using the binding energy of GTP to elicit release of inactive cofactor that is occasionally formed during the catalytic cycle of MCM. The physiological relevance of this mechanism is demonstrated by a patient mutation in methylmalonyl-CoA mutase that does not impair the activity of this enzyme per se but corrupts both the fidelity of the cofactor-loading process and the ejection of inactive cofactor that forms occasionally during catalysis. Consequently, cofactor in the incorrect oxidation state gains access to the mutase active site and is not released if generated during catalysis, leading, respectively, to assembly and accumulation of inactive enzyme and resulting in methylmalonic aciduria.
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Identification of multidrug resistance protein 1 (MRP1/ABCC1) as a molecular gate for cellular export of cobalamin. Blood 2009; 115:1632-9. [PMID: 19897579 DOI: 10.1182/blood-2009-07-232587] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cobalamin (Cbl, vitamin B(12)) deficiency in humans is a cause of hematologic and neurologic disorders. We show here that the cellular export of Cbl, in contrast to the carrier- and receptor-dependent cellular import of Cbl, occurs by transmembrane transport of "free" Cbl. Screening of candidate transporters by cellular gene silencing showed a role in cellular Cbl efflux of the ATP-binding cassette (ABC)-drug transporter, ABCC1, alias multidrug resistance protein 1 (MRP1), which is present in the basolateral membrane of intestinal epithelium and in other cells. The ability of MRP1 to mediate ATP-dependent Cbl transport was confirmed by vesicular transport experiments, and a physiologic role of MRP1 in mammalian Cbl homeostasis is indicated by the phenotype of knockout mice with targeted disruption of MRP1. These animals have a reduced concentration of Cbl in plasma and in the storage organs liver and kidney. In contrast, Cbl accumulates in the terminal part of the intestine of these mice, suggesting a functional malabsorption because of a lower epithelial basolateral Cbl efflux. The identification of this Cbl export mechanism now allows the delineation of a coherent pathway for Cbl trafficking from food to the body cells.
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Banerjee R, Gherasim C, Padovani D. The tinker, tailor, soldier in intracellular B12 trafficking. Curr Opin Chem Biol 2009; 13:484-91. [PMID: 19665918 DOI: 10.1016/j.cbpa.2009.07.007] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 07/02/2009] [Accepted: 07/09/2009] [Indexed: 11/19/2022]
Abstract
The recognition of eight discrete genetic complementation groups among patients with inherited cobalamin disorders provided early insights into the complexity of a cofactor-processing pathway that supports only two known B(12)-dependent enzymes in mammals. With the identification of all eight genes now completed, biochemical interrogations of their functions have started and are providing novel insights into a trafficking pathway involving porters that tinker with and tailor the active cofactor forms and editors that ensure the fidelity of the cofactor loading process. The principles of sequestration and escorted delivery of a rare and reactive organometallic cofactor that are emerging from studies on B(12) might be of general relevance to other cofactor trafficking pathways.
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Affiliation(s)
- Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI 48109-5606, USA.
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Viola-Villegas N, Rabideau AE, Bartholomä M, Zubieta J, Doyle RP. Targeting the Cubilin Receptor through the Vitamin B12 Uptake Pathway: Cytotoxicity and Mechanistic Insight through Fluorescent Re(I) Delivery. J Med Chem 2009; 52:5253-61. [DOI: 10.1021/jm900777v] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - Amy E. Rabideau
- Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100
| | - Mark Bartholomä
- Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100
| | - Jon Zubieta
- Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100
| | - Robert P. Doyle
- Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100
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Sommer P, Uhlich NA, Reymond JL, Darbre T. A peptide dendrimer model for vitamin B12 transport proteins. Chembiochem 2008; 9:689-93. [PMID: 18297678 DOI: 10.1002/cbic.200700606] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Peter Sommer
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
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Waibel R, Treichler H, Schaefer NG, van Staveren DR, Mundwiler S, Kunze S, Küenzi M, Alberto R, Nüesch J, Knuth A, Moch H, Schibli R, Schubiger PA. New Derivatives of Vitamin B12 Show Preferential Targeting of Tumors. Cancer Res 2008; 68:2904-11. [DOI: 10.1158/0008-5472.can-07-6771] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Rapidly growing cells show an increased demand for nutrients and vitamins. The objective of our work is to exploit the supply route of vitamin B12 to deliver new derivatives of this vital vitamin to hyperproliferative cells. To date, radiolabeled (57Co and 111In) vitamin B12 derivatives showed labeling of tumor tissue but also undesired high accumulation of radioactivity in normal tissue. By abolishing the interaction of a tailored vitamin B12 derivative to its transport protein transcobalamin II and therefore interrupting transcobalamin II receptor and megalin mediated uptake in normal tissue, preferential accumulation of a radiolabeled vitamin in cancer tissue could be accomplished. We identified transcobalamin I on tumors as a possible new receptor for this preferential accumulation of vitamin-mediated targeting. The low systemic distribution of radioactivity and the high tumor to blood ratio opens the possibility of a more successful clinical application of vitamin B12 for imaging or therapy. [Cancer Res 2008;68(8):2904–11]
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Affiliation(s)
- Robert Waibel
- 1Center for Radiopharmaceutical Science, Paul Scherrer Institute, Villigen PSI, Switzerland
| | | | | | - Dave R. van Staveren
- 1Center for Radiopharmaceutical Science, Paul Scherrer Institute, Villigen PSI, Switzerland
| | | | - Susanne Kunze
- 4Department of Inorganic Chemistry, University of Zurich
| | | | - Roger Alberto
- 4Department of Inorganic Chemistry, University of Zurich
| | | | | | - Holger Moch
- 5Institute of Surgical Pathology, Department Pathology, University Hospital of Zurich; and
| | - Roger Schibli
- 1Center for Radiopharmaceutical Science, Paul Scherrer Institute, Villigen PSI, Switzerland
- 6Department of Chemistry and Applied Biosciences of the Eidgenössische Technische Hochschule Zürich, Zurich, Switzerland; and
| | - Pius August Schubiger
- 1Center for Radiopharmaceutical Science, Paul Scherrer Institute, Villigen PSI, Switzerland
- 6Department of Chemistry and Applied Biosciences of the Eidgenössische Technische Hochschule Zürich, Zurich, Switzerland; and
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Duléry V, Uhlich NA, Maillard N, Fluxá VS, Garcia J, Dumy P, Renaudet O, Reymond JL, Darbre T. A cyclodecapeptide ligand to vitamin B12. Org Biomol Chem 2008; 6:4134-41. [DOI: 10.1039/b811234g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Hardlei TF, Morkbak AL, Nexo E. Enzymatic extraction of cobalamin from monoclonal antibody captured haptocorrin and transcobalamin. Clin Biochem 2007; 40:1392-7. [DOI: 10.1016/j.clinbiochem.2007.09.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Revised: 09/03/2007] [Accepted: 09/14/2007] [Indexed: 10/22/2022]
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Wuerges J, Geremia S, Randaccio L. Structural study on ligand specificity of human vitamin B12 transporters. Biochem J 2007; 403:431-40. [PMID: 17274763 PMCID: PMC1876373 DOI: 10.1042/bj20061394] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Studies comparing the binding of genuine cobalamin (vitamin B12) to that of its natural or synthetic analogues have long established increasing ligand specificity in the order haptocorrin, transcobalamin and intrinsic factor, the high-affinity binding proteins involved in cobalamin transport in mammals. In the present study, ligand specificity was investigated from a structural point of view, for which comparative models of intrinsic factor and haptocorrin are produced based on the crystal structure of the homologous transcobalamin and validated by results of published binding assays. Many interactions between cobalamin and its binding site in the interface of the two domains are conserved among the transporters. A structural comparison suggests that the determinant of specificity regarding cobalamin ligands with modified nucleotide moiety resides in the beta-hairpin motif beta3-turn-beta4 of the smaller C-terminal domain. In haptocorrin, it provides hydrophobic contacts to the benzimidazole moiety through the apolar regions of Arg357, Trp359 and Tyr362. Together, these large side chains may compensate for the missing nucleotide upon cobinamide binding. Intrinsic factor possesses only the tryptophan residue and transcobalamin only the tyrosine residue, consistent with their low affinity for cobinamide. Relative affinity constants for other analogues are rationalized similarly by analysis of steric and electrostatic interactions with the three transporters. The structures also indicate that the C-terminal domain is the first site of cobalamin-binding since part of the beta-hairpin motif is trapped between the nucleotide moiety and the N-terminal domain in the final holo-proteins.
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Affiliation(s)
- Jochen Wuerges
- Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
| | - Silvano Geremia
- Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
- To whom correspondence should be addressed (email )
| | - Lucio Randaccio
- Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
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Hannibal L, Bunge SD, van Eldik R, Jacobsen DW, Kratky C, Gruber K, Brasch NE. X-ray structural characterization of imidazolylcobalamin and histidinylcobalamin: cobalamin models for aquacobalamin bound to the B12 transporter protein transcobalamin. Inorg Chem 2007; 46:3613-8. [PMID: 17407285 PMCID: PMC2755209 DOI: 10.1021/ic070022n] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The X-ray structures of imidazolylcobalamin (ImCbl) and histidinylcobalamin (HisCbl) are reported. These structures are of interest given that the recent structures of human and bovine transcobalamin prepared in their holo forms from aquacobalamin show a histidine residue of the metalloprotein bound at the beta-axial site of the cobalamin (Wuerges, J. et al. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 4386-4391). The beta-axial Co-N bond distances for ImCbl and HisCbl are 1.94(1) and 1.951(7) A, respectively. The alpha-axial Co-N bond distances to the 5,6-dimethylbenzimidazole are 2.01(1) and 1.979(8) A for ImCbl and HisCbl, respectively, and are typical for cobalamins with weak sigma-donor ligands at the beta-axial site. The corrin fold angles of 11.8(3) degrees (ImCbl) and 12.0(3) degrees (HisCbl) are smaller than those typically observed for cobalamins.
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Affiliation(s)
- Luciana Hannibal
- Department of Chemistry, Kent State University, Kent, Ohio 44242
- School of Biomedical Sciences, Kent State University, Kent, Ohio 44242
- Department of Cell Biology, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195
| | - Scott D. Bunge
- Department of Chemistry, Kent State University, Kent, Ohio 44242
| | - Rudi van Eldik
- Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Donald W. Jacobsen
- School of Biomedical Sciences, Kent State University, Kent, Ohio 44242
- Department of Cell Biology, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195
| | - Christoph Kratky
- Institute of Chemistry, University of Graz, A-8010 Graz, Austria
| | - Karl Gruber
- Institute of Chemistry, University of Graz, A-8010 Graz, Austria
| | - Nicola E. Brasch
- Department of Chemistry, Kent State University, Kent, Ohio 44242
- School of Biomedical Sciences, Kent State University, Kent, Ohio 44242
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Fedosov SN, Grissom CB, Fedosova NU, Moestrup SK, Nexø E, Petersen TE. Application of a fluorescent cobalamin analogue for analysis of the binding kinetics. A study employing recombinant human transcobalamin and intrinsic factor. FEBS J 2006; 273:4742-53. [PMID: 16984395 DOI: 10.1111/j.1742-4658.2006.05478.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Fluorescent probe rhodamine was appended to 5' OH-ribose of cobalamin (Cbl). The prepared conjugate, CBC, bound to the transporting proteins, intrinsic factor (IF) and transcobalamin (TC), responsible for the uptake of Cbl in an organism. Pronounced increase in fluorescence upon CBC attachment facilitated detailed kinetic analysis of Cbl binding. We found that TC had the same affinity for CBC and Cbl (K(d) = 5 x 10(-15) m), whereas interaction of CBC with the highly specific protein IF was more complex. For instance, CBC behaved normally in the partial reactions CBC + IF(30) and CBC + IF(20) when binding to the isolated IF fragments (domains). The ligand could also assemble them into a stable complex IF(30)-CBC-IF(20) with higher fluorescent signal. However, dissociation of IF(30)-CBC-IF(20) and IF-CBC was accelerated by factors of 3 and 20, respectively, when compared to the corresponding Cbl complexes. We suggest that the correct domain-domain interactions are the most important factor during recognition and fixation of the ligands by IF. Dissociation of IF-CBC was biphasic, and existence of multiple protein-analogue complexes with normal and partially corrupted structure may explain this behaviour. The most stable component had K(d) = 1.5 x 10(-13) m, which guarantees the binding of CBC to IF under physiological conditions. The specific intestinal receptor cubilin bound both IF-CBC and IF-Cbl with equal affinity. In conclusion, the fluorescent analogue CBC can be used as a reporting agent in the kinetic studies, moreover, it seems to be applicable for imaging purposes in vivo.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Denmark.
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42
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Broderick KE, Feala J, McCulloch A, Paternostro G, Sharma VS, Pilz RB, Boss GR. The nitric oxide scavenger cobinamide profoundly improves survival in a Drosophila melanogaster model of bacterial sepsis. FASEB J 2006; 20:1865-73. [PMID: 16940158 DOI: 10.1096/fj.06-5780com] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Septic shock has an extremely high mortality rate, with approximately 200,000 people dying from sepsis annually in the U.S. The high mortality results in part from severe hypotension secondary to high serum NO concentrations. Reducing NO levels should be beneficial in sepsis, but NOS inhibitors have had a checkered history in animal models, and one such agent increased mortality in a clinical trial. An alternative approach to reduce NO levels in sepsis is to use an NO scavenger, which should leave sufficient free NO for normal physiological functions. Using a well-established model of bacterial sepsis in Drosophila melanogaster, we found that cobinamide, a B(12) analog and an effective NO scavenger in vitro, dramatically improved fly survival. Cobinamide augmented the effect of an antibiotic and was beneficial even in immune-deficient flies. Cobinamide's mechanism of action appeared to be from reducing NO levels and improving cardiac function.
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Affiliation(s)
- Kate E Broderick
- Department of Medicine, University of California San Diego, La Jolla 92093-0652, USA
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Abstract
Many coenzymes are vitamins that are assimilated in mammals into their active form from precursors obtained from the diet. They are often both rare and reactive rendering the likelihood low that the cell uses a collision-based strategy for their delivery to dependent enzymes. In humans, there are only two known B12 or cobalamin-dependent enzymes: methionine synthase and methylmalonyl-CoA mutase. However, the pathway for intracellular assimilation and utilization of this cofactor is complex as revealed by careful clinical analyses of fibroblasts from patients with disorders of cobalamin metabolism. In the recent past, six of the eight human genes involved in the B12 pathway have been identified and these have yielded important insights into their roles. The recent literature on the encoded proteins is reviewed, and a model for intracellular B12 trafficking is proposed in which B12 is escorted to its target proteins in the cytoplasmic and mitochondrial compartments in complex with chaperones, thereby averting problems of dilution and adventitious side reactions.
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Affiliation(s)
- Ruma Banerjee
- Redox Biology Center and the Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588-0664, USA.
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45
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Wuerges J, Garau G, Geremia S, Fedosov SN, Petersen TE, Randaccio L. Structural basis for mammalian vitamin B12 transport by transcobalamin. Proc Natl Acad Sci U S A 2006; 103:4386-91. [PMID: 16537422 PMCID: PMC1450181 DOI: 10.1073/pnas.0509099103] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Indexed: 11/18/2022] Open
Abstract
Cobalamin (Cbl, vitamin B(12)) serves for two essential cofactors in mammals. The pathway for its intestinal absorption, plasma transport, and cellular uptake uses cell surface receptors and three Cbl-transporting proteins, haptocorrin, intrinsic factor, and transcobalamin (TC). We present the structure determination of a member of the mammalian Cbl-transporter family. The crystal structures of recombinant human and bovine holo-TCs reveal a two-domain architecture, with an N-terminal alpha(6)-alpha(6) barrel and a smaller C-terminal domain. One Cbl molecule in base-on conformation is buried inside the domain interface. Structural data combined with previous binding assays indicate a domain motion in the first step of Cbl binding. In a second step, the weakly coordinated ligand H(2)O at the upper axial side of added H(2)O-Cbl is displaced by a histidine residue of the alpha(6)-alpha(6) barrel. Analysis of amino acid conservation on TC's surface in orthologous proteins suggests the location of the TC-receptor-recognition site in an extended region on the alpha(6)-alpha(6) barrel. The TC structure allows for the mapping of sites of amino acid variation due to polymorphisms of the human TC gene. Structural information is used to predict the overall fold of haptocorrin and intrinsic factor and permits a rational approach to the design of new Cbl-based bioconjugates for diagnostic or therapeutic drug delivery.
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Affiliation(s)
- Jochen Wuerges
- *Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy; and
| | - Gianpiero Garau
- *Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy; and
| | - Silvano Geremia
- *Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy; and
| | - Sergey N. Fedosov
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Science Park, Gustav Wieds Vey 10, 8000 Aarhus C, Denmark
| | - Torben E. Petersen
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Science Park, Gustav Wieds Vey 10, 8000 Aarhus C, Denmark
| | - Lucio Randaccio
- *Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy; and
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Butler P, Ebert MO, Lyskowski A, Gruber K, Kratky C, Kräutler B. Vitamin B12: A Methyl Group without a Job? Angew Chem Int Ed Engl 2006; 45:989-93. [PMID: 16374787 DOI: 10.1002/anie.200502638] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Philip Butler
- Institute of Organic Chemistry, Innrain 52a, Leopold-Franzens-Universität Innsbruck, Austria
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47
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Butler P, Ebert MO, Lyskowski A, Gruber K, Kratky C, Kräutler B. Vitamin B12: eine Methylgruppe ohne Aufgabe? Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200502638] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Affiliation(s)
- Kenneth L Brown
- Department of Chemistry and Biochemistry, Ohio University, Athens, 45701, USA.
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49
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Mundwiler S, Waibel R, Spingler B, Kunze S, Alberto R. Picolylamine-methylphosphonic acid esters as tridentate ligands for the labeling of alcohols with the fac-[M(CO)3]+ core (M=99mTc, Re): synthesis and biodistribution of model compounds and of a 99mTc-labeled cobinamide. Nucl Med Biol 2005; 32:473-84. [PMID: 15982578 DOI: 10.1016/j.nucmedbio.2005.04.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Revised: 04/06/2005] [Accepted: 04/12/2005] [Indexed: 11/28/2022]
Abstract
[(Methyl-pyridin-2-ylmethyl-amino)-methyl]-phosphonic acid is a new bifunctional chelator for the fac-[(99m)Tc(CO(3))](+) core which can be linked to biomolecules via formation of phosphonic acid esters. Its synthesis and the coupling to model alcohols and to a bioactive molecule (cobinamide) are described. The rhenium complexes [Re(CO)(3)L] of the esters have been prepared and characterized, one of them by X-ray crystallography. The model esters could be labeled with [(99m)Tc(OH(2))(3)(CO)(3)](+) under mild conditions and relatively low ligand concentration with >97% yield and only one isomer formed. The (99m)Tc-labeled cobinamide analog was a mixture of four isomers. It bound strongly to transcobalamin I (TC I, haptocorrin) but only slightly to transcobalamin II (TC II) and intrinsic factor (IF), reflecting the binding abilities of cobinamide. Biodistribution studies in mice with B(16) melanoma exhibited fast clearance with no specific tissue binding.
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Affiliation(s)
- Stefan Mundwiler
- Institute of Inorganic Chemistry, University of Zürich, Switzerland
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Broderick KE, Singh V, Zhuang S, Kambo A, Chen JC, Sharma VS, Pilz RB, Boss GR. Nitric Oxide Scavenging by the Cobalamin Precursor Cobinamide. J Biol Chem 2005; 280:8678-85. [PMID: 15632180 DOI: 10.1074/jbc.m410498200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitric oxide (NO) is an important signaling molecule, and a number of NO synthesis inhibitors and scavengers have been developed to allow study of NO functions and to reduce excess NO levels in disease states. We showed previously that cobinamide, a cobalamin (vitamin B12) precursor, binds NO with high affinity, and we now evaluated the potential of cobinamide as a NO scavenger in biologic systems. We found that cobinamide reversed NO-stimulated fluid secretion in Drosophila Malpighian tubules, both when applied in the form of a NO donor and when produced intracellularly by nitricoxide synthase. Moreover, feeding flies cobinamide markedly attenuated subsequent NO-induced increases in tubular fluid secretion. Cobinamide was taken up efficiently by cultured rodent cells and prevented NO-induced phosphorylation of the vasodilator-stimulated phosphoprotein VASP both when NO was provided to the cells and when NO was generated intracellularly. Cobinamide appeared to act via scavenging NO because it reduced nitrite and nitrate concentrations in both the fly and mammalian cell systems, and it did not interfere with cGMP-induced phosphorylation of VASP. In rodent and human cells, cobinamide exhibited toxicity at concentrations > or =50 microM with toxicity completely prevented by providing equimolar amounts of cobalamin. Combining cobalamin with cobinamide had no effect on the ability of cobinamide to scavenge NO. Cobinamide did not inhibit the in vitro activity of either of the two mammalian cobalamin-dependent enzymes, methionine synthase or methylmalonyl-coenzyme A mutase; however, it did inhibit the in vivo activities of the enzymes in the absence, but not presence, of cobalamin, suggesting that cobinamide toxicity was secondary to interference with cobalamin metabolism. As part of these studies, we developed a facile method for producing and purifying cobinamide. We conclude that cobinamide is an effective intra- and extracellular NO scavenger whose modest toxicity can be eliminated by cobalamin.
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Affiliation(s)
- Kate E Broderick
- Department of Medicine and Cancer Center, University of California, San Diego, La Jolla, California 92093-0652, USA
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