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Pilic J, Gottschalk B, Bourgeois B, Habisch H, Koshenov Z, Oflaz FE, Erdogan YC, Miri SM, Yiğit EN, Aydın MŞ, Öztürk G, Eroglu E, Shoshan-Barmatz V, Madl T, Graier WF, Malli R. Hexokinase 1 forms rings that regulate mitochondrial fission during energy stress. Mol Cell 2024; 84:2732-2746.e5. [PMID: 38981483 DOI: 10.1016/j.molcel.2024.06.009] [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: 09/29/2023] [Revised: 04/30/2024] [Accepted: 06/11/2024] [Indexed: 07/11/2024]
Abstract
Metabolic enzymes can adapt during energy stress, but the consequences of these adaptations remain understudied. Here, we discovered that hexokinase 1 (HK1), a key glycolytic enzyme, forms rings around mitochondria during energy stress. These HK1-rings constrict mitochondria at contact sites with the endoplasmic reticulum (ER) and mitochondrial dynamics protein (MiD51). HK1-rings prevent mitochondrial fission by displacing the dynamin-related protein 1 (Drp1) from mitochondrial fission factor (Mff) and mitochondrial fission 1 protein (Fis1). The disassembly of HK1-rings during energy restoration correlated with mitochondrial fission. Mechanistically, we identified that the lack of ATP and glucose-6-phosphate (G6P) promotes the formation of HK1-rings. Mutations that affect the formation of HK1-rings showed that HK1-rings rewire cellular metabolism toward increased TCA cycle activity. Our findings highlight that HK1 is an energy stress sensor that regulates the shape, connectivity, and metabolic activity of mitochondria. Thus, the formation of HK1-rings may affect mitochondrial function in energy-stress-related pathologies.
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Affiliation(s)
- Johannes Pilic
- Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstraße 6/4, 8010 Graz, Austria
| | - Benjamin Gottschalk
- Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstraße 6/4, 8010 Graz, Austria
| | - Benjamin Bourgeois
- BioTechMed Graz, Mozartgasse 12/2, 8010 Graz, Austria; Otto Loewi Research Center, Medical Chemistry, Medical University of Graz, 8010 Graz, Austria
| | - Hansjörg Habisch
- Otto Loewi Research Center, Medical Chemistry, Medical University of Graz, 8010 Graz, Austria
| | - Zhanat Koshenov
- Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstraße 6/4, 8010 Graz, Austria
| | - Furkan E Oflaz
- Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstraße 6/4, 8010 Graz, Austria
| | - Yusuf C Erdogan
- Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstraße 6/4, 8010 Graz, Austria
| | - Seyed M Miri
- Regenerative and Restorative Medicine Research Center (REMER), Research Institute for Health Sciences and Technologies (SABITA), Istanbul Medipol University, 34810 Istanbul, Türkiye; Molecular Biology, Genetics and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, 34956 Istanbul, Türkiye
| | - Esra N Yiğit
- Regenerative and Restorative Medicine Research Center (REMER), Research Institute for Health Sciences and Technologies (SABITA), Istanbul Medipol University, 34810 Istanbul, Türkiye; Department of Physiology, International School of Medicine, Istanbul Medipol University, 34810 Istanbul, Türkiye
| | - Mehmet Ş Aydın
- Regenerative and Restorative Medicine Research Center (REMER), Research Institute for Health Sciences and Technologies (SABITA), Istanbul Medipol University, 34810 Istanbul, Türkiye
| | - Gürkan Öztürk
- Regenerative and Restorative Medicine Research Center (REMER), Research Institute for Health Sciences and Technologies (SABITA), Istanbul Medipol University, 34810 Istanbul, Türkiye
| | - Emrah Eroglu
- Regenerative and Restorative Medicine Research Center (REMER), Research Institute for Health Sciences and Technologies (SABITA), Istanbul Medipol University, 34810 Istanbul, Türkiye; Department of Physiology, International School of Medicine, Istanbul Medipol University, 34810 Istanbul, Türkiye
| | - Varda Shoshan-Barmatz
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, 84105 Beer-Sheva, Israel
| | - Tobias Madl
- BioTechMed Graz, Mozartgasse 12/2, 8010 Graz, Austria; Otto Loewi Research Center, Medical Chemistry, Medical University of Graz, 8010 Graz, Austria
| | - Wolfgang F Graier
- Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstraße 6/4, 8010 Graz, Austria; BioTechMed Graz, Mozartgasse 12/2, 8010 Graz, Austria
| | - Roland Malli
- Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Neue Stiftingtalstraße 6/4, 8010 Graz, Austria; BioTechMed Graz, Mozartgasse 12/2, 8010 Graz, Austria; Center for Medical Research, CF Bioimaging, Medical University of Graz, Neue Stiftingtalstraße 6/6, 8010 Graz, Austria.
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Dillenberger M, Werner AD, Velten AS, Rahlfs S, Becker K, Fritz-Wolf K. Structural Analysis of Plasmodium falciparum Hexokinase Provides Novel Information about Catalysis Due to a Plasmodium-Specific Insertion. Int J Mol Sci 2023; 24:12739. [PMID: 37628920 PMCID: PMC10454665 DOI: 10.3390/ijms241612739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 08/10/2023] [Accepted: 08/10/2023] [Indexed: 08/27/2023] Open
Abstract
The protozoan parasite Plasmodium falciparum is the causative pathogen of the most severe form of malaria, for which novel strategies for treatment are urgently required. The primary energy supply for intraerythrocytic stages of Plasmodium is the production of ATP via glycolysis. Due to the parasite's strong dependence on this pathway and the significant structural differences of its glycolytic enzymes compared to its human counterpart, glycolysis is considered a potential drug target. In this study, we provide the first three-dimensional protein structure of P. falciparum hexokinase (PfHK) containing novel information about the mechanisms of PfHK. We identified for the first time a Plasmodium-specific insertion that lines the active site. Moreover, we propose that this insertion plays a role in ATP binding. Residues of the insertion further seem to affect the tetrameric interface and therefore suggest a special way of communication among the different monomers. In addition, we confirmed that PfHK is targeted and affected by oxidative posttranslational modifications (oxPTMs). Both S-glutathionylation and S-nitrosation revealed an inhibitory effect on the enzymatic activity of PfHK.
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Affiliation(s)
- Melissa Dillenberger
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University, D-35392 Giessen, Germany; (M.D.)
| | - Anke-Dorothee Werner
- Institute of Virology, University of Marburg, Hans-Meerwein-Str. 2, D-35043 Marburg, Germany
| | - Ann-Sophie Velten
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University, D-35392 Giessen, Germany; (M.D.)
| | - Stefan Rahlfs
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University, D-35392 Giessen, Germany; (M.D.)
| | - Katja Becker
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University, D-35392 Giessen, Germany; (M.D.)
| | - Karin Fritz-Wolf
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University, D-35392 Giessen, Germany; (M.D.)
- Max-Planck Institute for Medical Research, Jahnstr. 29, D-69120 Heidelberg, Germany
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Veiga-da-Cunha M, Wortmann SB, Grünert SC, Van Schaftingen E. Treatment of the Neutropenia Associated with GSD1b and G6PC3 Deficiency with SGLT2 Inhibitors. Diagnostics (Basel) 2023; 13:diagnostics13101803. [PMID: 37238286 DOI: 10.3390/diagnostics13101803] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/12/2023] [Accepted: 05/17/2023] [Indexed: 05/28/2023] Open
Abstract
Glycogen storage disease type Ib (GSD1b) is due to a defect in the glucose-6-phosphate transporter (G6PT) of the endoplasmic reticulum, which is encoded by the SLC37A4 gene. This transporter allows the glucose-6-phosphate that is made in the cytosol to cross the endoplasmic reticulum (ER) membrane and be hydrolyzed by glucose-6-phosphatase (G6PC1), a membrane enzyme whose catalytic site faces the lumen of the ER. Logically, G6PT deficiency causes the same metabolic symptoms (hepatorenal glycogenosis, lactic acidosis, hypoglycemia) as deficiency in G6PC1 (GSD1a). Unlike GSD1a, GSD1b is accompanied by low neutrophil counts and impaired neutrophil function, which is also observed, independently of any metabolic problem, in G6PC3 deficiency. Neutrophil dysfunction is, in both diseases, due to the accumulation of 1,5-anhydroglucitol-6-phosphate (1,5-AG6P), a potent inhibitor of hexokinases, which is slowly formed in the cells from 1,5-anhydroglucitol (1,5-AG), a glucose analog that is normally present in blood. Healthy neutrophils prevent the accumulation of 1,5-AG6P due to its hydrolysis by G6PC3 following transport into the ER by G6PT. An understanding of this mechanism has led to a treatment aimed at lowering the concentration of 1,5-AG in blood by treating patients with inhibitors of SGLT2, which inhibits renal glucose reabsorption. The enhanced urinary excretion of glucose inhibits the 1,5-AG transporter, SGLT5, causing a substantial decrease in the concentration of this polyol in blood, an increase in neutrophil counts and function and a remarkable improvement in neutropenia-associated clinical signs and symptoms.
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Affiliation(s)
- Maria Veiga-da-Cunha
- Metabolic Research Group, de Duve Institute and UCLouvain, B-1200 Brussels, Belgium
| | - Saskia B Wortmann
- University Children's Hospital, Paracelsus Medical University, 5020 Salzburg, Austria
- Amalia Children's Hospital, Radboudumc, 6525 Nijmegen, The Netherlands
| | - Sarah C Grünert
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Center, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
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De novo variants in HK1 associated with neurodevelopmental abnormalities and visual impairment. Eur J Hum Genet 2019; 27:1081-1089. [PMID: 30778173 DOI: 10.1038/s41431-019-0366-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 12/15/2018] [Accepted: 02/02/2019] [Indexed: 12/18/2022] Open
Abstract
Hexokinase 1 (HK1) phosphorylates glucose to glucose-6-phosphate, the first rate-limiting step in glycolysis. Homozygous and heterozygous variants in HK1 have been shown to cause autosomal recessive non-spherocytic hemolytic anemia, autosomal recessive Russe type hereditary motor and sensory neuropathy, and autosomal dominant retinitis pigmentosa (adRP). We report seven patients from six unrelated families with a neurodevelopmental disorder associated with developmental delay, intellectual disability, structural brain abnormality, and visual impairments in whom we identified four novel, de novo missense variants in the N-terminal half of HK1. Hexokinase activity in red blood cells of two patients was normal, suggesting that the disease mechanism is not due to loss of hexokinase enzymatic activity.
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Calmettes G, Ribalet B, John S, Korge P, Ping P, Weiss JN. Hexokinases and cardioprotection. J Mol Cell Cardiol 2014; 78:107-15. [PMID: 25264175 DOI: 10.1016/j.yjmcc.2014.09.020] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/10/2014] [Accepted: 09/16/2014] [Indexed: 12/17/2022]
Abstract
As mediators of the first enzymatic step in glucose metabolism, hexokinases (HKs) orchestrate a variety of catabolic and anabolic uses of glucose, regulate antioxidant power by generating NADPH for glutathione reduction, and modulate cell death processes by directly interacting with the voltage-dependent anion channel (VDAC), a regulatory component of the mitochondrial permeability transition pore (mPTP). Here we summarize the current state-of-knowledge about HKs and their role in protecting the heart from ischemia/reperfusion (I/R) injury, reviewing: 1) the properties of different HK isoforms and how their function is regulated by their subcellular localization; 2) how HKs modulate glucose metabolism and energy production during I/R; 3) the molecular mechanisms by which HKs influence mPTP opening and cellular injury during I/R; and 4) how different metabolic and HK profiles correlate with susceptibility to I/R injury and cardioprotective efficacy in cancer cells, neonatal hearts, and normal, hypertrophied and failing adult hearts, and how these difference may guide novel therapeutic strategies to limit I/R injury in the heart. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease".
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Affiliation(s)
- Guillaume Calmettes
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Bernard Ribalet
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Scott John
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Paavo Korge
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Peipei Ping
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - James N Weiss
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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Sullivan LS, Koboldt DC, Bowne SJ, Lang S, Blanton SH, Cadena E, Avery CE, Lewis RA, Webb-Jones K, Wheaton DH, Birch DG, Coussa R, Ren H, Lopez I, Chakarova C, Koenekoop RK, Garcia CA, Fulton RS, Wilson RK, Weinstock GM, Daiger SP. A dominant mutation in hexokinase 1 (HK1) causes retinitis pigmentosa. Invest Ophthalmol Vis Sci 2014; 55:7147-58. [PMID: 25190649 DOI: 10.1167/iovs.14-15419] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To identify the cause of retinitis pigmentosa (RP) in UTAD003, a large, six-generation Louisiana family with autosomal dominant retinitis pigmentosa (adRP). METHODS A series of strategies, including candidate gene screening, linkage exclusion, genome-wide linkage mapping, and whole-exome next-generation sequencing, was used to identify a mutation in a novel disease gene on chromosome 10q22.1. Probands from an additional 404 retinal degeneration families were subsequently screened for mutations in this gene. RESULTS Exome sequencing in UTAD003 led to identification of a single, novel coding variant (c.2539G>A, p.Glu847Lys) in hexokinase 1 (HK1) present in all affected individuals and absent from normal controls. One affected family member carries two copies of the mutation and has an unusually severe form of disease, consistent with homozygosity for this mutation. Screening of additional adRP probands identified four other families (American, Canadian, and Sicilian) with the same mutation and a similar range of phenotypes. The families share a rare 450-kilobase haplotype containing the mutation, suggesting a founder mutation among otherwise unrelated families. CONCLUSIONS We identified an HK1 mutation in five adRP families. Hexokinase 1 catalyzes phosphorylation of glucose to glucose-6-phosphate. HK1 is expressed in retina, with two abundant isoforms expressed at similar levels. The Glu847Lys mutation is located at a highly conserved position in the protein, outside the catalytic domains. We hypothesize that the effect of this mutation is limited to the retina, as no systemic abnormalities in glycolysis were detected. Prevalence of the HK1 mutation in our cohort of RP families is 1%.
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Affiliation(s)
- Lori S Sullivan
- Human Genetics Center, University of Texas Health Science Center, Houston, Texas, United States
| | - Daniel C Koboldt
- The Genome Institute at Washington University, St. Louis, Missouri, United States
| | - Sara J Bowne
- Human Genetics Center, University of Texas Health Science Center, Houston, Texas, United States
| | - Steven Lang
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, Florida, United States
| | - Susan H Blanton
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, Florida, United States
| | - Elizabeth Cadena
- Human Genetics Center, University of Texas Health Science Center, Houston, Texas, United States
| | - Cheryl E Avery
- Human Genetics Center, University of Texas Health Science Center, Houston, Texas, United States
| | - Richard A Lewis
- Departments of Ophthalmology, Medicine, Pediatrics, and Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States
| | - Kaylie Webb-Jones
- The Retina Foundation of the Southwest, Dallas, Texas, United States
| | - Dianna H Wheaton
- The Retina Foundation of the Southwest, Dallas, Texas, United States
| | - David G Birch
- The Retina Foundation of the Southwest, Dallas, Texas, United States
| | - Razck Coussa
- McGill Ocular Genetics Laboratory, Departments of Paediatric Surgery, Human Genetics, and Ophthalmology, McGill University Health Center, Montreal, Quebec, Canada
| | - Huanan Ren
- McGill Ocular Genetics Laboratory, Departments of Paediatric Surgery, Human Genetics, and Ophthalmology, McGill University Health Center, Montreal, Quebec, Canada
| | - Irma Lopez
- McGill Ocular Genetics Laboratory, Departments of Paediatric Surgery, Human Genetics, and Ophthalmology, McGill University Health Center, Montreal, Quebec, Canada
| | - Christina Chakarova
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Robert K Koenekoop
- McGill Ocular Genetics Laboratory, Departments of Paediatric Surgery, Human Genetics, and Ophthalmology, McGill University Health Center, Montreal, Quebec, Canada
| | - Charles A Garcia
- Department of Ophthalmology and Visual Sciences, University of Texas Health Science Center, Houston, Texas, United States
| | - Robert S Fulton
- The Genome Institute at Washington University, St. Louis, Missouri, United States
| | - Richard K Wilson
- The Genome Institute at Washington University, St. Louis, Missouri, United States
| | - George M Weinstock
- The Genome Institute at Washington University, St. Louis, Missouri, United States
| | - Stephen P Daiger
- Human Genetics Center, University of Texas Health Science Center, Houston, Texas, United States Department of Ophthalmology and Visual Sciences, University of Texas Health Science Center, Houston, Texas, United States
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Zhang F, Wang L, Zhang C, Zhao Y. Novel regio- and stereoselective phosphonyl radical addition to glycals promoted by Mn(ii)–air: syntheses of 1,2-dideoxy 2-C-diphenylphosphinylglycopyranosides. Chem Commun (Camb) 2014; 50:2046-8. [DOI: 10.1039/c3cc48806c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The novel Mn(ii)–air promoted radical reaction of diphenylphosphine oxide with various glycals in excellent regio- and stereoselectivities generated 1,2-dideoxy-2-C-diphenylphosphinylglycopyranosides.
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Affiliation(s)
- Fuyi Zhang
- The College of Chemistry and Molecular Engineering
- The Key Lab of Chemical Biology and Organic Chemistry
- Zhengzhou University
- Zhengzhou 450052, China
| | - Liming Wang
- The College of Chemistry and Molecular Engineering
- The Key Lab of Chemical Biology and Organic Chemistry
- Zhengzhou University
- Zhengzhou 450052, China
| | - Cui Zhang
- The College of Chemistry and Molecular Engineering
- The Key Lab of Chemical Biology and Organic Chemistry
- Zhengzhou University
- Zhengzhou 450052, China
| | - Yufen Zhao
- The College of Chemistry and Molecular Engineering
- The Key Lab of Chemical Biology and Organic Chemistry
- Zhengzhou University
- Zhengzhou 450052, China
- College of Chemistry and Chemical Engineering
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8
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Yuan C, Hollingsworth RI. A short and efficient synthesis of 1,5-anhydro-d-glucitol 6-phosphate. Tetrahedron Lett 2011. [DOI: 10.1016/j.tetlet.2011.07.082] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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John S, Weiss JN, Ribalet B. Subcellular localization of hexokinases I and II directs the metabolic fate of glucose. PLoS One 2011; 6:e17674. [PMID: 21408025 PMCID: PMC3052386 DOI: 10.1371/journal.pone.0017674] [Citation(s) in RCA: 169] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 02/11/2011] [Indexed: 11/30/2022] Open
Abstract
Background The first step in glucose metabolism is conversion of glucose to glucose 6-phosphate (G-6-P) by hexokinases (HKs), a family with 4 isoforms. The two most common isoforms, HKI and HKII, have overlapping tissue expression, but different subcellular distributions, with HKI associated mainly with mitochondria and HKII associated with both mitochondrial and cytoplasmic compartments. Here we tested the hypothesis that these different subcellular distributions are associated with different metabolic roles, with mitochondrially-bound HK's channeling G-6-P towards glycolysis (catabolic use), and cytoplasmic HKII regulating glycogen formation (anabolic use). Methodology/Principal Findings To study subcellular translocation of HKs in living cells, we expressed HKI and HKII linked to YFP in CHO cells. We concomitantly recorded the effects on glucose handling using the FRET based intracellular glucose biosensor, FLIPglu-600 mM, and glycogen formation using a glycogen-associated protein, PTG, tagged with GFP. Our results demonstrate that HKI remains strongly bound to mitochondria, whereas HKII translocates between mitochondria and the cytosol in response to glucose, G-6-P and Akt, but not ATP. Metabolic measurements suggest that HKI exclusively promotes glycolysis, whereas HKII has a more complex role, promoting glycolysis when bound to mitochondria and glycogen synthesis when located in the cytosol. Glycogen breakdown upon glucose removal leads to HKII inhibition and dissociation from mitochondria, probably mediated by increases in glycogen-derived G-6-P. Conclusions/Significance These findings show that the catabolic versus anabolic fate of glucose is dynamically regulated by extracellular glucose via signaling molecules such as intracellular glucose, G-6-P and Akt through regulation and subcellular translocation of HKII. In contrast, HKI, which activity and regulation is much less sensitive to these factors, is mainly committed to glycolysis. This may be an important mechanism by which HK's allow cells to adapt to changing metabolic conditions to maintain energy balance and avoid injury.
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Affiliation(s)
- Scott John
- UCLA Cardiovascular Research Laboratory, Department of Medicine (Cardiology), David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America
| | - James N. Weiss
- UCLA Cardiovascular Research Laboratory, Department of Physiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America
- UCLA Cardiovascular Research Laboratory, Department of Medicine (Cardiology), David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America
| | - Bernard Ribalet
- UCLA Cardiovascular Research Laboratory, Department of Physiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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Chilcot J, Wellsted D, Da Silva-Gane M, Farrington K. Depression on dialysis. Nephron Clin Pract 2008; 108:c256-64. [PMID: 18401193 DOI: 10.1159/000124749] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Depression is the most common psychopathological condition among patients with end-stage renal disease (ESRD), yet it is still under-recognized and misdiagnosed. Depression reduces quality of life and has a negative clinical impact upon sufferers with chronic illness, including ESRD. This article discusses the negative effects of depression among the ESRD population treated with dialysis, the prevalence of the condition, the methodological issues involved with screening and treatment, and the possible psychological and somatic causes. There is a need to identify the prevalence of the disorder by effective methods, overcome the current issues surrounding depression assessment and to undertake trials of suitable treatments.
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Skaff DA, Kim CS, Tsai HJ, Honzatko RB, Fromm HJ. Glucose 6-phosphate release of wild-type and mutant human brain hexokinases from mitochondria. J Biol Chem 2005; 280:38403-9. [PMID: 16166083 DOI: 10.1074/jbc.m506943200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
One molecule of glucose 6-phosphate inhibits brain hexokinase (HKI) with high affinity by binding to either one of two sites located in distinct halves of the enzyme. In addition to potent inhibition, glucose 6-phosphate releases HKI from the outer leaflet of mitochondria; however, the site of glucose 6-phosphate association responsible for the release of HKI is unclear. The incorporation of a C-terminal polyhistidine tag on HKI facilitates the rapid purification of recombinant enzyme from Escherichia coli. The tagged construct has N-formyl methionine as its first residue and has mitochondrial association properties comparable with native brain hexokinases. Release of wild-type and mutant hexokinases from mitochondria by glucose 6-phosphate follow equilibrium models, which explain the release phenomenon as the repartitioning of ligand-bound HKI between solution and the membrane. Mutations that block the binding of glucose 6-phosphate to the C-terminal half of HKI have little or no effect on the glucose 6-phosphate release. In contrast, mutations that block glucose 6-phosphate binding to the N-terminal half require approximately 7-fold higher concentrations of glucose 6-phosphate for the release of HKI. Results here implicate a primary role for the glucose 6-phosphate binding site at the N-terminal half of HKI in the release mechanism.
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Affiliation(s)
- D Andrew Skaff
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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Andreoni F, Serafini G, Laguardia ME, Magnani M. Bovine hexokinase type I: full-length cDNA sequence and characterisation of the recombinant enzyme. Mol Cell Biochem 2005; 268:9-18. [PMID: 15724432 DOI: 10.1007/s11010-005-1846-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This study reports the revised and full-length cDNA sequence of bovine hexokinase type I obtained from bovine brain. Since dissimilarities have been observed between the published bovine hexokinase type I coding sequence (GenBank accession no. M65140) (Genomics 11: 1014-1024, 1991) and an analysed portion of bovine hexokinase type I gene, the entire open reading frame was re-sequenced and the ends of cDNA isolated by rapid amplification of cDNA ends. The coding sequences, when compared with the published bovine hexokinase type I, contained a large number of mismatches that lead to changes in the resulting amino acid sequence. The revisions result in a hexokinase type I cDNA of 3619 bp that encodes a protein of 917 amino acids highly homologous to human hexokinase type I. The expression of the recombinant full-length enzyme demonstrated that it was a catalytically active hexokinase. When characterised for its kinetic and regulatory properties, it displayed the same affinity for glucose and MgATP as the human hexokinase type I and was inhibited by glucose 6-phosphate competitively versus MgATP. The production of the N- and C-terminal recombinant halves of the enzyme followed by comparison with the full-length hexokinase indicated that the catalytic activity is located in the C-terminal domain.
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Mukai T, Kawai S, Mori S, Mikami B, Murata K. Crystal Structure of Bacterial Inorganic Polyphosphate/ATP-glucomannokinase. J Biol Chem 2004; 279:50591-600. [PMID: 15377666 DOI: 10.1074/jbc.m408126200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inorganic polyphosphate (poly(P)) is a biological high energy compound presumed to be an ancient energy carrier preceding ATP. Several poly(P)-dependent kinases that use poly(P) as a phosphoryl donor are known to function in bacteria, but crystal structures of these kinases have not been solved. Here we present the crystal structure of bacterial poly(P)/ATP-glucomannokinase, belonging to Gram-positive bacterial glucokinase, complexed with 1 glucose molecule and 2 phosphate molecules at 1.8 A resolution, being the first among poly(P)-dependent kinases and bacterial glucokinases. The poly(P)/ATP-glucomannokinase structure enabled us to understand the structural relationship of bacterial glucokinase to eucaryotic hexokinase and ADP-glucokinase, which has remained a matter of debate. These comparisons also enabled us to propose putative binding sites for phosphoryl groups for ATP and especially for poly(P) and to obtain insights into the evolution of kinase, particularly from primordial poly(P)-specific to ubiquitous ATP-specific proteins.
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Affiliation(s)
- Takako Mukai
- Department of Basic and Applied Molecular Biotechnology, Division of Food and Biological Science, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
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14
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van Wijk R, Rijksen G, Huizinga EG, Nieuwenhuis HK, van Solinge WW. HK Utrecht: missense mutation in the active site of human hexokinase associated with hexokinase deficiency and severe nonspherocytic hemolytic anemia. Blood 2003; 101:345-7. [PMID: 12393545 DOI: 10.1182/blood-2002-06-1851] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hexokinase deficiency is a rare autosomal recessive disease with a clinical phenotype of severe hemolysis. We report a novel homozygous missense mutation in exon 15 (c.2039C>G, HK [hexokinase] Utrecht) of HK1, the gene that encodes red blood cell-specific hexokinase-R, in a patient previously diagnosed with hexokinase deficiency. The Thr680Ser substitution predicted by this mutation affects a highly conserved residue in the enzyme's active site that interacts with phosphate moieties of adenosine diphosphate, adenosine triphosphate (ATP), and inhibitor glucose-6-phosphate. We correlated the molecular data to the severe clinical phenotype of the patient by means of altered enzymatic properties of partially purified hexokinase from the patient, notably with respect to Mg(2+)-ATP binding. These kinetic properties contradict those obtained from a recombinant mutant brain hexokinase-I with the same Thr680Ser substitution. This contradiction thereby stresses the valuable contribution of studying patients with hexokinase deficiency to achieve a better understanding of hexokinase's key role in glycolysis.
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Affiliation(s)
- Richard van Wijk
- Department of Clinical Chemistry and the Department of Hematology, University Medical Center Utrecht, The Netherlands
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15
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Saito T, Maeda T, Nakazawa M, Takeuchi T, Nozaki T, Asai T. Characterisation of hexokinase in Toxoplasma gondii tachyzoites. Int J Parasitol 2002; 32:961-7. [PMID: 12076625 DOI: 10.1016/s0020-7519(02)00059-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We have cloned the hexokinase [E.C. 2.7.1.1] gene of Toxoplasma gondii tachyzoite and obtained an active recombinant enzyme with a calculated molecular mass of 51,465Da and an isoelectric point of 5.82. Southern blot analysis indicated that the hexokinase gene existed as a single copy in the tachyzoites of T. gondii. The sequence of T. gondii hexokinase exhibited the highest identity (44%) to that of Plasmodium falciparum hexokinase and lower identity of less than 35% to those of hexokinases from other organisms. The specific activity of the homogeneously purified recombinant enzyme was 4.04 micromol/mg protein/min at 37 degrees C under optimal conditions. The enzyme could use glucose, fructose, and mannose as substrates, though it preferred glucose. Adenosine triphosphate was exclusively the most effective phosphorus donor, and pyrophosphate did not serve as a substrate. K(m) values for glucose and adenosine triphosphate were 8.0+/-0.8 microM and 1.05+/-0.25mM, respectively. No allosteric effect of substrates was observed, and the products, glucose 6-phosphate and adenosine diphosphate, had no inhibitory effect on T. gondii hexokinase activity. Other phosphorylated hexoses, fructose 6-phosphate, trehalose 6-phosphate which is an inhibitor of yeast hexokinase, and pyrophosphate, also did not affect T. gondii hexokinase activity. Native hexokinase activity was recovered in both the cytosol and membrane fractions of the whole lysate of T. gondii tachyzoites. This result suggests that T. gondii hexokinase weakly associates with the membrane or particulate fraction of the tachyzoite cell.
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Affiliation(s)
- Tomoya Saito
- Department of Tropical Medicine and Parasitology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
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16
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Hashimoto M, Wilson JE. Kinetic and regulatory properties of HK I(+), a modified form of the type I isozyme of mammalian hexokinase in which interactions between the N- and C-terminal halves have been disrupted. Arch Biochem Biophys 2002; 399:109-15. [PMID: 11883910 DOI: 10.1006/abbi.2001.2744] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A modified form (HK I(+)) of rat Type I hexokinase (HK I) has been expressed. HK I(+) contains a centrally located polyalanine insert which, along with the known helical propensity of adjacent sequence, was expected to lead to alpha-helix formation, with resulting distension of the molecule and disruption of interactions between the N- and C-terminal halves. The properties of HK I(+) are consistent with this expectation and with previous proposals that (1) inhibition of HK I by Glc-6-P or its analogs and antagonism of this inhibition by P(i) result from competition of these ligands for a binding site in the N-terminal half of HK I, with resulting conformational changes propagated through interactions with the catalytic C-terminal half, and (2) binding of Glc-6-P to a site in the C-terminal half of HK I is obstructed by interactions between the halves, present in HK I but not HK I(+).
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Affiliation(s)
- Mitsuru Hashimoto
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA
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17
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Muñoz-Alonso MJ, Guillemain G, Kassis N, Girard J, Burnol AF, Leturque A. A novel cytosolic dual specificity phosphatase, interacting with glucokinase, increases glucose phosphorylation rate. J Biol Chem 2000; 275:32406-12. [PMID: 10913113 DOI: 10.1074/jbc.m000841200] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A novel protein was cloned from a rat liver cDNA library by interaction with the liver glucokinase. This protein contained 339 residues and possessed a canonical consensus sequence for a dual specificity phosphatase. The recombinant protein was able to dephosphorylate phosphotyrosyl and phosphoseryl/threonyl substrates. We called this protein the glucokinase-associated phosphatase (GKAP). The GKAP partially dephosphorylated the recombinant glucokinase previously phosphorylated, in vitro, by protein kinase A. The GKAP fused with green fluorescent protein was located in the cytosol, where glucokinase phosphorylates glucose, and not in the nucleus where the glucokinase is retained inactive by the glucokinase regulatory protein. More importantly, the GKAP accelerated the glucokinase activity in a dose-dependent manner and with a stoichiometry compatible with a physiological mechanism. This strongly suggested that the interaction between GKAP and glucokinase had a functional significance. The cloning of this novel protein with a dual specificity phosphatase activity allows the description of a possible new regulatory step in controlling the glycolysis flux.
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Affiliation(s)
- M J Muñoz-Alonso
- CNRS UPR 1524, 9, rue Jules Hetzel, 92190 Meudon, INSERM U505, 15 rue de l'Ecole de Médecine, 75006 Paris, France
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18
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Aleshin AE, Kirby C, Liu X, Bourenkov GP, Bartunik HD, Fromm HJ, Honzatko RB. Crystal structures of mutant monomeric hexokinase I reveal multiple ADP binding sites and conformational changes relevant to allosteric regulation. J Mol Biol 2000; 296:1001-15. [PMID: 10686099 DOI: 10.1006/jmbi.1999.3494] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hexokinase I, the pacemaker of glycolysis in brain tissue, is composed of two structurally similar halves connected by an alpha-helix. The enzyme dimerizes at elevated protein concentrations in solution and in crystal structures; however, almost all published data reflect the properties of a hexokinase I monomer in solution. Crystal structures of mutant forms of recombinant human hexokinase I, presented here, reveal the enzyme monomer for the first time. The mutant hexokinases bind both glucose 6-phosphate and glucose with high affinity to their N and C-terminal halves, and ADP, also with high affinity, to a site near the N terminus of the polypeptide chain. Exposure of the monomer crystals to ADP in the complete absence of glucose 6-phosphate reveals a second binding site for adenine nucleotides at the putative active site (C-half), with conformational changes extending 15 A to the contact interface between the N and C-halves. The structures reveal distinct conformational states for the C-half and a rigid-body rotation of the N-half, as possible elements of a structure-based mechanism for allosteric regulation of catalysis.
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Affiliation(s)
- A E Aleshin
- Department of Biochemistry Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
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19
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Rosano C, Sabini E, Rizzi M, Deriu D, Murshudov G, Bianchi M, Serafini G, Magnani M, Bolognesi M. Binding of non-catalytic ATP to human hexokinase I highlights the structural components for enzyme-membrane association control. Structure 1999; 7:1427-37. [PMID: 10574795 DOI: 10.1016/s0969-2126(00)80032-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Hexokinase I sets the pace of glycolysis in the brain, catalyzing the ATP-dependent phosphorylation of glucose. The catalytic properties of hexokinase I are dependent on product inhibition as well as on the action of phosphate. In vivo, a large fraction of hexokinase I is bound to the mitochondrial outer membrane, where the enzyme adopts a tetrameric assembly. The mitochondrion-bound hexokinase I is believed to optimize the ATP/ADP exchange between glucose phosphorylation and the mitochondrial oxidative phosphorylation reactions. RESULTS The crystal structure of human hexokinase I has been determined at 2.25 A resolution. The overall structure of the enzyme is in keeping with the closed conformation previously observed in yeast hexokinase. One molecule of the ATP analogue AMP-PNP is bound to each N-terminal domain of the dimeric enzyme in a surface cleft, showing specific interactions with the nucleotide, and localized positive electrostatic potential. The molecular symmetry brings the two bound AMP-PNP molecules, at the centre of two extended surface regions, to a common side of the dimeric hexokinase I molecule. CONCLUSIONS The binding of AMP-PNP to a protein site separated from the catalytic centre of human hexokinase I can be related to the role played by some nucleotides in dissociating the enzyme from the mitochondrial membrane, and helps in defining the molecular regions of hexokinase I that are expected to be in contact with the mitochondrion. The structural information presented here is in keeping with monoclonal antibody mapping of the free and mitochondrion-bound forms of the enzyme, and with sequence analysis of hexokinases that differ in their mitochondria binding properties.
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Affiliation(s)
- C Rosano
- Dipartimento di Fisica - INFM, Centro Biotecnologie Avanzate - IST, Universita' di Genova, Genova, 10. I-16132, Italy
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20
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Liu X, Kim CS, Kurbanov FT, Honzatko RB, Fromm HJ. Dual mechanisms for glucose 6-phosphate inhibition of human brain hexokinase. J Biol Chem 1999; 274:31155-9. [PMID: 10531306 DOI: 10.1074/jbc.274.44.31155] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Brain hexokinase (HKI) is inhibited potently by its product glucose 6-phosphate (G6P); however, the mechanism of inhibition is unsettled. Two hypotheses have been proposed to account for product inhibition of HKI. In one, G6P binds to the active site (the C-terminal half of HKI) and competes directly with ATP, whereas in the alternative suggestion the inhibitor binds to an allosteric site (the N-terminal half of HKI), which indirectly displaces ATP from the active site. Single mutations within G6P binding pockets, as defined by crystal structures, at either the N- or C-terminal half of HKI have no significant effect on G6P inhibition. On the other hand, the corresponding mutations eliminate product inhibition in a truncated form of HKI, consisting only of the C-terminal half of the enzyme. Only through combined mutations at the active and allosteric sites, using residues for which single mutations had little effect, was product inhibition eliminated in HKI. Evidently, potent inhibition of HKI by G6P can occur from both active and allosteric binding sites. Furthermore, kinetic data reported here, in conjunction with published equilibrium binding data, are consistent with inhibitory sites of comparable affinity linked by a mechanism of negative cooperativity.
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Affiliation(s)
- X Liu
- Department of Biochemistry, Iowa State University, Ames, Iowa 50011, USA
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21
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Ardehali H, Printz RL, Whitesell RR, May JM, Granner DK. Functional interaction between the N- and C-terminal halves of human hexokinase II. J Biol Chem 1999; 274:15986-9. [PMID: 10347146 DOI: 10.1074/jbc.274.23.15986] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian hexokinases (HKs) I-III are composed of two highly homologous approximately 50-kDa halves. Studies of HKI indicate that the C-terminal half of the molecule is active and is sensitive to inhibition by glucose 6-phosphate (G6P), whereas the N-terminal half binds G6P but is devoid of catalytic activity. In contrast, both the N- and C-terminal halves of HKII (N-HKII and C-HKII, respectively) are catalytically active, and when expressed as discrete proteins both are inhibited by G6P. However, C-HKII has a significantly higher Ki for G6P (KiG6P) than N-HKII. We here address the question of whether the high KiG6P of the C-terminal half (C-half) of HKII is decreased by interaction with the N-terminal half (N-half) in the context of the intact enzyme. A chimeric protein consisting of the N-half of HKI and the C-half of HKII was prepared. Because the N-half of HKI is unable to phosphorylate glucose, the catalytic activity of this chimeric enzyme depends entirely on the C-HKII component. The KiG6P of this chimeric enzyme is similar to that of HKI and is significantly lower than that of C-HKII. When a conserved amino acid (Asp209) required for glucose binding is mutated in the N-half of this chimeric protein, a significantly higher KiG6P (similar to that of C-HKII) is observed. However, mutation of a second conserved amino acid (Ser155), also involved in catalysis but not required for glucose binding, does not increase the KiG6P of the chimeric enzyme. This resembles the behavior of HKII, in which a D209A mutation results in an increase in the KiG6P of the enzyme, whereas a S155A mutation does not. These results suggest an interaction in which glucose binding by the N-half causes the activity of the C-half to be regulated by significantly lower concentrations of G6P.
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Affiliation(s)
- H Ardehali
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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22
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Sebastian S, Wilson JE, Mulichak A, Garavito RM. Allosteric regulation of type I hexokinase: A site-directed mutational study indicating location of the functional glucose 6-phosphate binding site in the N-terminal half of the enzyme. Arch Biochem Biophys 1999; 362:203-10. [PMID: 9989928 DOI: 10.1006/abbi.1998.1043] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Type I isozyme of mammalian hexokinase has evolved by a gene duplication-fusion mechanism, with resulting internal duplication of sequence and ligand binding sites. However, 1:1 binding stoichiometry indicates that only one of these is available for binding the product inhibitor, Glc-6-P; the location of that site, in the N- or C-terminal half, remains under debate. Recent structural studies (Aleshin et al., Structure 6, 39-50, 1998; Mulichak et al., Nature Struct. Biol. 5, 555-560, 1998) implicated Asp 84 or its analog in the C-terminal half, Asp 532, in binding of Glc-6-P. Zeng et al. (Biochemistry 35, 13157-13164, 1996) demonstrated that mutation of Asp 532 to Lys or Glu did not affect inhibition by the Glc-6-P analog, 1,5-anhydroglucitol-6-P. These same mutations, as well as mutation to Ala, at the Asp 84 position are now shown to result in increased Ki for 1,5-anhydroglucitol-6-P. The ability of Pi to antagonize inhibition by the Glc-6-P analog is severely diminished or abolished by these mutations, suggesting that antagonism is dependent on precise positioning of the inhibitory hexose 6-phosphate. The structure of the enzyme complexed with Glc and Pi has been determined, and shows that Pi occupies the same site as the 6-phosphate group in the complex with Glc-6-P. Thus, antagonism between these ligands results from competition for a common anion binding site in the N-terminal half.
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Affiliation(s)
- S Sebastian
- Department of Biochemistry, Michigan State University, East Lansing, Michigan, 48824-1319, USA
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23
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Aleshin AE, Zeng C, Bartunik HD, Fromm HJ, Honzatko RB. Regulation of hexokinase I: crystal structure of recombinant human brain hexokinase complexed with glucose and phosphate. J Mol Biol 1998; 282:345-57. [PMID: 9735292 DOI: 10.1006/jmbi.1998.2017] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hexokinase I, the pacemaker of glycolysis in brain tissue and red blood cells, is comprised of two similar domains fused into a single polypeptide chain. The C-terminal half of hexokinase I is catalytically active, whereas the N-terminal half is necessary for the relief of product inhibition by phosphate. A crystalline complex of recombinant human hexokinase I with glucose and phosphate (2.8 A resolution) reveals a single binding site for phosphate and glucose at the N-terminal half of the enzyme. Glucose and phosphate stabilize the N-terminal half in a closed conformation. Unexpectedly, glucose binds weakly to the C-terminal half of the enzyme and does not by itself stabilize a closed conformation. Evidently a stable, closed C-terminal half requires either ATP or glucose 6-phosphate along with glucose. The crystal structure here, in conjunction with other studies in crystallography and directed mutation, puts the phosphate regulatory site at the N-terminal half, the site of potent product inhibition at the C-terminal half, and a secondary site for the weak interaction of glucose 6-phosphate at the N-terminal half of the enzyme. The relevance of crystal structures of hexokinase I to the properties of monomeric hexokinase I and oligomers of hexokinase I bound to the surface of mitochondria is discussed.
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Affiliation(s)
- A E Aleshin
- Department of Biochemistry and Biophysics, Iowa State University, Ames, IA 50011, USA
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