1
|
Henriques BJ, Katrine Jentoft Olsen R, Gomes CM, Bross P. Electron transfer flavoprotein and its role in mitochondrial energy metabolism in health and disease. Gene 2021; 776:145407. [PMID: 33450351 DOI: 10.1016/j.gene.2021.145407] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 12/08/2020] [Accepted: 12/16/2020] [Indexed: 12/15/2022]
Abstract
Electron transfer flavoprotein (ETF) is an enzyme with orthologs from bacteria to humans. Human ETF is nuclear encoded by two separate genes, ETFA and ETFB, respectively. After translation, the two subunits are imported to the mitochondrial matrix space and assemble into a heterodimer containing one FAD and one AMP as cofactors. ETF functions as a hub taking up electrons from at least 14 flavoenzymes, feeding them into the respiratory chain. This represents a major source of reducing power for the electron transport chain from fatty acid oxidation and amino acid degradation. Transfer of electrons from the donor enzymes to ETF occurs by direct transfer between the enzyme bound flavins, a process that is tightly regulated by the polypeptide chain and by protein:protein interactions. ETF, in turn relays electrons to the iron sulfur cluster of the inner membrane protein ETF:QO, from where they travel via the FAD in ETF:QO to ubiquinone, entering the respiratory chain at the level of complex III. ETF recognizes its dehydrogenase partners via a recognition loop that anchors the protein on its partner followed by dynamic movements of the ETF flavin domain that bring redox cofactors in close proximity, thus promoting electron transfer. Genetic mutations in the ETFA or ETFB genes cause the Mendelian disorder multiple acyl-CoA dehydrogenase deficiency (MADD; OMIM #231680). We here review the knowledge on human ETF and investigations of the effects of disease-associated missense mutations in this protein that have promoted the understanding of the essential role that ETF plays in cellular metabolism and human disease.
Collapse
Affiliation(s)
- Bárbara J Henriques
- Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal; Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
| | - Rikke Katrine Jentoft Olsen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, 8200 Aarhus, Denmark.
| | - Cláudio M Gomes
- Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal; Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
| | - Peter Bross
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, 8200 Aarhus, Denmark.
| |
Collapse
|
2
|
Henriques BJ, Lucas TG, Martins E, Gaspar A, Bandeira A, Nogueira C, Brandão O, Rocha H, Vilarinho L, Gomes CM. Molecular and Clinical Investigations on Portuguese Patients with Multiple acyl-CoA Dehydrogenase Deficiency. Curr Mol Med 2020; 19:487-493. [PMID: 31418342 DOI: 10.2174/1566524019666190507114748] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 04/08/2019] [Accepted: 04/09/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND Multiple Acyl-CoA Dehydrogenase Deficiency (MADD) is a congenital rare metabolic disease with broad clinical phenotypes and variable evolution. This inborn error of metabolism is caused by mutations in the ETFA, ETFB or ETFDH genes, which encode for the mitochondrial ETF and ETF:QO proteins. A considerable group of patients has been described to respond positively to riboflavin oral supplementation, which constitutes the prototypic treatment for the pathology. OBJECTIVES To report mutations in ETFA, ETFB and ETFDH genes identified in Portuguese patients, correlating, whenever possible, biochemical and clinical outcomes with the effects of mutations on the structure and stability of the affected proteins, to better understand MADD pathogenesis at the molecular level. METHODS MADD patients were identified based on the characteristic urinary profile of organic acids and/or acylcarnitine profiles in blood spots during newborn screening. Genotypic, clinical and biochemical data were collected for all patients. In silico structural analysis was employed using bioinformatic tools carried out in an ETF:QO molecular model for the identified missense mutations. RESULTS A survey describing clinical and biochemical features of eight Portuguese MADD patients was made. Genotype analysis identified five ETFDH mutations, including one extension (p.X618QextX*14), two splice mutations (c.34+5G>C and c.405+3A>T) and two missense mutations (ETF:QO-p.Arg155Gly and ETF:QO-p.Pro534Leu), and one ETFB mutation (ETFβ- p.Arg191Cys). Homozygous patients containing the ETFDH mutations p.X618QextX*14, c.34+5G>C and ETF:QO-p.Arg155Gly, all presented severe (lethal) MADD phenotypes. However, when any of these mutations are in heterozygosity with the known ETF:QO-p.Pro534Leu mild variant, the severe clinical effects are partly and temporarily attenuated. Indeed, the latter destabilizes an ETF-interacting loop, with no major functional consequences. However, the position 155 in ETF:QO is localized at the ubiquinone binding and membrane interacting domain, and is thus expected to perturb protein structure and membrane insertion, with severe functional effects. Structural analysis of molecular models is therefore demonstrated to be a valuable tool to rationalize the effects of mutations in the context of the clinical phenotype severity. CONCLUSION Advanced molecular diagnosis, structural analysis and clinical correlations reveal that MADD patients harboring a severe prognosis mutation in one allele can actually revert to a milder phenotype by complementation with a milder mutation in the other allele. However, such patients are nevertheless in a precarious metabolic balance which can revert to severe fatal outcomes during catabolic stress or secondary pathology, thus requiring strict clinical follow-up.
Collapse
Affiliation(s)
- Bárbara J Henriques
- Biosystems and Integrative Sciences Institute, Faculdade de Ciencias, Universidade de Lisboa, and Departamento de Quimica e Bioquimica, Faculdade de Ciencias, 1749-016 Lisboa, Portugal
| | - Tânia G Lucas
- Biosystems and Integrative Sciences Institute, Faculdade de Ciencias, Universidade de Lisboa, and Departamento de Quimica e Bioquimica, Faculdade de Ciencias, 1749-016 Lisboa, Portugal
| | - Esmeralda Martins
- Centro de Referencia na area de Doencas Hereditarias do Metabolismo, Centro Hospitalar do Porto - CHP, Porto, Portugal
| | - Ana Gaspar
- Unidade de Doencas Metabolicas, Centro Hospitalar Lisboa Norte - Hospital Santa Maria, Lisboa, Portugal
| | - Anabela Bandeira
- Centro de Referencia na area de Doencas Hereditarias do Metabolismo, Centro Hospitalar do Porto - CHP, Porto, Portugal
| | - Célia Nogueira
- Unidade de Rastreio Neonatal, Metabolismo e Genetica, Departamento de Genetica Humana - Instituto Nacional de Saude Doutor Ricardo Jorge, Porto, Portugal
| | - Otilia Brandão
- Servico de Patologia Clinica, Hospital Sao Joao, Porto, Portugal
| | - Hugo Rocha
- Unidade de Rastreio Neonatal, Metabolismo e Genetica, Departamento de Genetica Humana - Instituto Nacional de Saude Doutor Ricardo Jorge, Porto, Portugal
| | - Laura Vilarinho
- Unidade de Rastreio Neonatal, Metabolismo e Genetica, Departamento de Genetica Humana - Instituto Nacional de Saude Doutor Ricardo Jorge, Porto, Portugal
| | - Cláudio M Gomes
- Biosystems and Integrative Sciences Institute, Faculdade de Ciencias, Universidade de Lisboa, and Departamento de Quimica e Bioquimica, Faculdade de Ciencias, 1749-016 Lisboa, Portugal
| |
Collapse
|
3
|
Lucas TG, Henriques BJ, Gomes CM. Conformational analysis of the riboflavin-responsive ETF:QO-p.Pro456Leu variant associated with mild multiple acyl-CoA dehydrogenase deficiency. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2020; 1868:140393. [PMID: 32087359 DOI: 10.1016/j.bbapap.2020.140393] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 02/09/2020] [Accepted: 02/17/2020] [Indexed: 01/07/2023]
Abstract
Multiple-CoA dehydrogenase deficiency (MADD) is an inborn disorder of fatty acid and amino acid metabolism caused by mutations in the genes encoding for human electron transfer flavoprotein (ETF) and its partner electron transfer flavoprotein:ubiquinone oxidoreductase (ETF:QO). Albeit a rare disease, extensive newborn screening programs contributed to a wider coverage of MADD genotypes. However, the impact of non-lethal mutations on ETF:QO function remains scarcely understood from a structural perspective. To this end, we here revisit the relatively common MADD mutation ETF:QO-p.Pro456Leu, in order to clarify how it affects enzyme structure and folding. Given the limitation in recombinant expression of human ETF:QO, we resort to its bacterial homologue from Rhodobacter sphaeroides (Rs), in which the corresponding mutation (p.Pro389Leu) was inserted. The in vitro biochemical and biophysical investigations of the Rs ETF:QO-p.Pro389Leu variant showed that, while the mutation does not significantly affect the protein α/β fold, it introduces some plasticity on the tertiary structure and within flavin interactions. Indeed, in the p.Pro389Leu variant, FAD exhibits a higher thermolability during thermal denaturation and a faster rate of release in temperature-induced dissociation experiments, in comparison to the wild type. Therefore, although this clinical mutation occurs in the ubiquinone domain, its effect likely propagates to the nearby FAD binding domain, probably influencing electron transfer and redox potentials. Overall, our results provide a molecular rational for the decreased enzyme activity observed in patients and suggest that compromised FAD interactions in ETF:QO might account for the known riboflavin responsiveness of this mutation.
Collapse
Affiliation(s)
- Tânia G Lucas
- Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Bárbara J Henriques
- Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Cláudio M Gomes
- Biosystems and Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
| |
Collapse
|
4
|
Chronic Hypoxia Enhances β-Oxidation-Dependent Electron Transport via Electron Transferring Flavoproteins. Cells 2019; 8:cells8020172. [PMID: 30781698 PMCID: PMC6406996 DOI: 10.3390/cells8020172] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 02/14/2019] [Accepted: 02/15/2019] [Indexed: 01/22/2023] Open
Abstract
Hypoxia poses a stress to cells and decreases mitochondrial respiration, in part by electron transport chain (ETC) complex reorganization. While metabolism under acute hypoxia is well characterized, alterations under chronic hypoxia largely remain unexplored. We followed oxygen consumption rates in THP-1 monocytes during acute (16 h) and chronic (72 h) hypoxia, compared to normoxia, to analyze the electron flows associated with glycolysis, glutamine, and fatty acid oxidation. Oxygen consumption under acute hypoxia predominantly demanded pyruvate, while under chronic hypoxia, fatty acid- and glutamine-oxidation dominated. Chronic hypoxia also elevated electron-transferring flavoproteins (ETF), and the knockdown of ETF–ubiquinone oxidoreductase lowered mitochondrial respiration under chronic hypoxia. Metabolomics revealed an increase in citrate under chronic hypoxia, which implied glutamine processing to α-ketoglutarate and citrate. Expression regulation of enzymes involved in this metabolic shunting corroborated this assumption. Moreover, the expression of acetyl-CoA carboxylase 1 increased, thus pointing to fatty acid synthesis under chronic hypoxia. Cells lacking complex I, which experienced a markedly impaired respiration under normoxia, also shifted their metabolism to fatty acid-dependent synthesis and usage. Taken together, we provide evidence that chronic hypoxia fuels the ETC via ETFs, increasing fatty acid production and consumption via the glutamine-citrate-fatty acid axis.
Collapse
|
5
|
Ampawong S, Isarangkul D, Reamtong O, Aramwit P. Adaptive effect of sericin on hepatic mitochondrial conformation through its regulation of apoptosis, autophagy and energy maintenance: a proteomics approach. Sci Rep 2018; 8:14943. [PMID: 30297713 PMCID: PMC6175853 DOI: 10.1038/s41598-018-33372-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 09/27/2018] [Indexed: 12/22/2022] Open
Abstract
We recently demonstrated that in addition to its protective effect on pancreatic and adrenal biosynthesis, antioxidant properties of sericin decrease blood cholesterol levels and improve the liver mitochondrial architecture. However, little is known about the detailed mechanisms underlying these effects. Using proteomics and electron microscopy, we identified mitochondrial proteins that play important roles in the preservation of the mitochondrial ultrastructure and cholesterol-lowering properties of sericin. Our results showed that sericin maintains the mitochondrial architecture during conditions of high blood cholesterol by regulating apoptotic (NADH-ubiquinone oxidoreductase 75 kDa subunit) and autophagic (mitochondrial elongation factor Tu and prohibitin-2) proteins as well as energy maintenance proteins [haloacid dehalogenase-like hydrolase domain-containing protein 3, succinate dehydrogenase (ubiquinone) flavoprotein subunit, ATP synthase-α subunit precursor, enoyl-CoA hydratase domain-containing protein 3 and electron transfer flavoprotein subunit-α]. Sericin also exerts anti-oxidative properties via aconitate hydratase and Chain A, crystal structure of rat carnitine palmitoyltrasferase 2 proteins. Together, these activities may reduce hepatocytic triglyceride deposition, thereby decreasing steatosis, as demonstrated by the modulatory effects on ornithine aminotransferase, mitochondrial aspartate aminotransferase, acyl-CoA synthase, hydroxyacyl-CoA dehydrogenase and D-beta-hydroxybutyrate dehydrogenase. Sericin activity further balanced nitrogenous waste detoxification, characterised by carbamoyl-phosphate synthase (ammonia), aldehyde dehydrogenase and uricase, or folate biosynthesis via sarcosine dehydrogenase and dimethyl glycine dehydrogenase. These results suggest that sericin maintains the hepatic mitochondrial architecture through apoptotic, autophagic, energy maintenance and anti-oxidative mitochondrial proteins for alleviating hepatic steatosis and promoting liver function under conditions of hypercholesterolaemia.
Collapse
Affiliation(s)
- Sumate Ampawong
- Department of Tropical Pathology, Faculty of Tropical Medicine, Mahidol University, Ratchawithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Duangnate Isarangkul
- Department of Microbiology, Faculty of Science, Mahidol University, 272, Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Onrapak Reamtong
- Department of Molecular Tropical Medicine and Genetic, Faculty of Tropical Medicine, Mahidol University, Ratchawithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Pornanong Aramwit
- Bioactive Resources for Innovative Clinical Applications Research Unit and Department of Pharmacy Practice, Faculty of Pharmaceutical Sciences, Chulalongkorn University, PhayaThai Road, Phatumwan, Bangkok, 10330, Thailand.
| |
Collapse
|
6
|
Mitochondrial β-oxidation of saturated fatty acids in humans. Mitochondrion 2018; 46:73-90. [PMID: 29551309 DOI: 10.1016/j.mito.2018.02.009] [Citation(s) in RCA: 186] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 12/04/2017] [Accepted: 02/27/2018] [Indexed: 12/30/2022]
Abstract
Mitochondrial β-oxidation of fatty acids generates acetyl-coA, NADH and FADH2. Acyl-coA synthetases catalyze the binding of fatty acids to coenzyme A to form fatty acyl-coA thioesters, the first step in the intracellular metabolism of fatty acids. l-carnitine system facilitates the transport of fatty acyl-coA esters across the mitochondrial membrane. Carnitine palmitoyltransferase-1 transfers acyl groups from coenzyme A to l-carnitine, forming acyl-carnitine esters at the outer mitochondrial membrane. Carnitine acyl-carnitine translocase exchanges acyl-carnitine esters that enter the mitochondria, by free l-carnitine. Carnitine palmitoyltransferase-2 converts acyl-carnitine esters back to acyl-coA esters at the inner mitochondrial membrane. The β-oxidation pathway of fatty acyl-coA esters includes four reactions. Fatty acyl-coA dehydrogenases catalyze the introduction of a double bond at the C2 position, producing 2-enoyl-coA esters and reducing equivalents that are transferred to the respiratory chain via electron transferring flavoprotein. Enoyl-coA hydratase catalyzes the hydration of the double bond to generate a 3-l-hydroxyacyl-coA derivative. 3-l-hydroxyacyl-coA dehydrogenase catalyzes the formation of a 3-ketoacyl-coA intermediate. Finally, 3-ketoacyl-coA thiolase catalyzes the cleavage of the chain, generating acetyl-coA and a fatty acyl-coA ester two carbons shorter. Mitochondrial trifunctional protein catalyzes the three last steps in the β-oxidation of long-chain and medium-chain fatty acyl-coA esters while individual enzymes catalyze the β-oxidation of short-chain fatty acyl-coA esters. Clinical phenotype of fatty acid oxidation disorders usually includes hypoketotic hypoglycemia triggered by fasting or infections, skeletal muscle weakness, cardiomyopathy, hepatopathy, and neurological manifestations. Accumulation of non-oxidized fatty acids promotes their conjugation with glycine and l-carnitine and alternate ways of oxidation, such as ω-oxidation.
Collapse
|
7
|
Duan HD, Lubner CE, Tokmina-Lukaszewska M, Gauss GH, Bothner B, King PW, Peters JW, Miller AF. Distinct properties underlie flavin-based electron bifurcation in a novel electron transfer flavoprotein FixAB from Rhodopseudomonas palustris. J Biol Chem 2018; 293:4688-4701. [PMID: 29462786 DOI: 10.1074/jbc.ra117.000707] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 02/08/2018] [Indexed: 11/06/2022] Open
Abstract
A newly recognized third fundamental mechanism of energy conservation in biology, electron bifurcation, uses free energy from exergonic redox reactions to drive endergonic redox reactions. Flavin-based electron bifurcation furnishes low-potential electrons to demanding chemical reactions, such as reduction of dinitrogen to ammonia. We employed the heterodimeric flavoenzyme FixAB from the diazotrophic bacterium Rhodopseudomonas palustris to elucidate unique properties that underpin flavin-based electron bifurcation. FixAB is distinguished from canonical electron transfer flavoproteins (ETFs) by a second FAD that replaces the AMP of canonical ETF. We exploited near-UV-visible CD spectroscopy to resolve signals from the different flavin sites in FixAB and to interrogate the putative bifurcating FAD. CD aided in assigning the measured reduction midpoint potentials (E° values) to individual flavins, and the E° values tested the accepted model regarding the redox properties required for bifurcation. We found that the higher-E° flavin displays sequential one-electron (1-e-) reductions to anionic semiquinone and then to hydroquinone, consistent with the reactivity seen in canonical ETFs. In contrast, the lower-E° flavin displayed a single two-electron (2-e-) reduction without detectable accumulation of semiquinone, consistent with unstable semiquinone states, as required for bifurcation. This is the first demonstration that a FixAB protein possesses the thermodynamic prerequisites for bifurcating activity, and the separation of distinct optical signatures for the two flavins lays a foundation for mechanistic studies to learn how electron flow can be directed in a protein environment. We propose that a novel optical signal observed at long wavelength may reflect electron delocalization between the two flavins.
Collapse
Affiliation(s)
- H Diessel Duan
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506
| | | | | | - George H Gauss
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717
| | - Brian Bothner
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717
| | - Paul W King
- National Renewable Energy Laboratory, Golden, Colorado 80401
| | - John W Peters
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99163
| | | |
Collapse
|
8
|
Olsen RKJ, Koňaříková E, Giancaspero TA, Mosegaard S, Boczonadi V, Mataković L, Veauville-Merllié A, Terrile C, Schwarzmayr T, Haack TB, Auranen M, Leone P, Galluccio M, Imbard A, Gutierrez-Rios P, Palmfeldt J, Graf E, Vianey-Saban C, Oppenheim M, Schiff M, Pichard S, Rigal O, Pyle A, Chinnery PF, Konstantopoulou V, Möslinger D, Feichtinger RG, Talim B, Topaloglu H, Coskun T, Gucer S, Botta A, Pegoraro E, Malena A, Vergani L, Mazzà D, Zollino M, Ghezzi D, Acquaviva C, Tyni T, Boneh A, Meitinger T, Strom TM, Gregersen N, Mayr JA, Horvath R, Barile M, Prokisch H. Riboflavin-Responsive and -Non-responsive Mutations in FAD Synthase Cause Multiple Acyl-CoA Dehydrogenase and Combined Respiratory-Chain Deficiency. Am J Hum Genet 2016; 98:1130-1145. [PMID: 27259049 PMCID: PMC4908180 DOI: 10.1016/j.ajhg.2016.04.006] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 04/13/2016] [Indexed: 12/27/2022] Open
Abstract
Multiple acyl-CoA dehydrogenase deficiencies (MADDs) are a heterogeneous group of metabolic disorders with combined respiratory-chain deficiency and a neuromuscular phenotype. Despite recent advances in understanding the genetic basis of MADD, a number of cases remain unexplained. Here, we report clinically relevant variants in FLAD1, which encodes FAD synthase (FADS), as the cause of MADD and respiratory-chain dysfunction in nine individuals recruited from metabolic centers in six countries. In most individuals, we identified biallelic frameshift variants in the molybdopterin binding (MPTb) domain, located upstream of the FADS domain. Inasmuch as FADS is essential for cellular supply of FAD cofactors, the finding of biallelic frameshift variants was unexpected. Using RNA sequencing analysis combined with protein mass spectrometry, we discovered FLAD1 isoforms, which only encode the FADS domain. The existence of these isoforms might explain why affected individuals with biallelic FLAD1 frameshift variants still harbor substantial FADS activity. Another group of individuals with a milder phenotype responsive to riboflavin were shown to have single amino acid changes in the FADS domain. When produced in E. coli, these mutant FADS proteins resulted in impaired but detectable FADS activity; for one of the variant proteins, the addition of FAD significantly improved protein stability, arguing for a chaperone-like action similar to what has been reported in other riboflavin-responsive inborn errors of metabolism. In conclusion, our studies identify FLAD1 variants as a cause of potentially treatable inborn errors of metabolism manifesting with MADD and shed light on the mechanisms by which FADS ensures cellular FAD homeostasis.
Collapse
MESH Headings
- Adult
- Blotting, Western
- Case-Control Studies
- Cells, Cultured
- Electron Transport
- Female
- Fibroblasts/drug effects
- Fibroblasts/metabolism
- Fibroblasts/pathology
- Flavin-Adenine Dinucleotide/metabolism
- Frameshift Mutation/genetics
- Gene Expression Profiling
- Humans
- Infant
- Infant, Newborn
- Liver/drug effects
- Liver/metabolism
- Liver/pathology
- Male
- Mitochondrial Diseases/drug therapy
- Mitochondrial Diseases/genetics
- Mitochondrial Diseases/pathology
- Multiple Acyl Coenzyme A Dehydrogenase Deficiency/drug therapy
- Multiple Acyl Coenzyme A Dehydrogenase Deficiency/genetics
- Multiple Acyl Coenzyme A Dehydrogenase Deficiency/pathology
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Mutagenesis, Site-Directed
- Nucleotidyltransferases/genetics
- Protein Binding
- RNA, Messenger/genetics
- Real-Time Polymerase Chain Reaction
- Reverse Transcriptase Polymerase Chain Reaction
- Riboflavin/pharmacology
- Skin/drug effects
- Skin/metabolism
- Skin/pathology
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- Vitamin B Complex/pharmacology
- Young Adult
Collapse
Affiliation(s)
- Rikke K J Olsen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and University Hospital, 8200 Aarhus N, Denmark.
| | - Eliška Koňaříková
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Teresa A Giancaspero
- Department of Biosciences, Biotechnology, and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Signe Mosegaard
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and University Hospital, 8200 Aarhus N, Denmark
| | - Veronika Boczonadi
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Lavinija Mataković
- Department of Paediatrics, Paracelsus Medical University, SALK Salzburg, 5020 Salzburg, Austria
| | - Alice Veauville-Merllié
- Service Maladies Héréditaires du Métabolisme et Dépistage Néonatal, Centre de Biologie et Pathologie Est, Centre Hospitalier Universitaire Lyon, 69500 Bron, France
| | - Caterina Terrile
- Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Thomas Schwarzmayr
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Tobias B Haack
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Mari Auranen
- Clinical Neurosciences, Neurology, University of Helsinki and Helsinki University Hospital, 340 Helsinki, Finland
| | - Piero Leone
- Department of Biosciences, Biotechnology, and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Michele Galluccio
- Department DiBEST (Biology, Ecology, and Earth Sciences), University of Calabria, 87036 Arcavacata di Rende, Italy
| | - Apolline Imbard
- Biochemistry Hormonology Laboratory, Robert-Debré Hospital, 75019 Paris, France; Pharmacy Faculty, Paris Sud University, 92019 Chatenay-Malabry, France
| | - Purificacion Gutierrez-Rios
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK; Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Johan Palmfeldt
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and University Hospital, 8200 Aarhus N, Denmark
| | - Elisabeth Graf
- Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Christine Vianey-Saban
- Service Maladies Héréditaires du Métabolisme et Dépistage Néonatal, Centre de Biologie et Pathologie Est, Centre Hospitalier Universitaire Lyon, 69500 Bron, France
| | - Marcus Oppenheim
- Neurometabolic Unit, National Hospital for Neurology and Neurosurgery, London WCIN 3BG, UK
| | - Manuel Schiff
- INSERM UMR 1141, Hôpital Robert Debré, 75019 Paris, France; Reference Center for Inherited Metabolic Diseases, Robert-Debré Hospital, Assistance Publique - Hôpitaux de Paris, 75019 Paris, France; Faculté de Médecine Denis Diderot, Université Paris Diderot (Paris 7), 75013 Paris, France
| | - Samia Pichard
- Reference Center for Inherited Metabolic Diseases, Robert-Debré Hospital, Assistance Publique - Hôpitaux de Paris, 75019 Paris, France
| | - Odile Rigal
- Biochemistry Hormonology Laboratory, Robert-Debré Hospital, 75019 Paris, France
| | - Angela Pyle
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Patrick F Chinnery
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK; Department of Clinical Neurosciences, Cambridge Biomedical Campus, University of Cambridge, Cambridge CB2 0QQ, UK
| | | | - Dorothea Möslinger
- Department of Pediatrics, Medical University of Vienna, 1090 Vienna, Austria
| | - René G Feichtinger
- Department of Paediatrics, Paracelsus Medical University, SALK Salzburg, 5020 Salzburg, Austria
| | - Beril Talim
- Pathology Unit, Department of Pediatrics, Hacettepe University Children's Hospital, 06100 Ankara, Turkey
| | - Haluk Topaloglu
- Neurology Unit, Department of Pediatrics, Hacettepe University Children's Hospital, 06100 Ankara, Turkey
| | - Turgay Coskun
- Metabolism Unit, Department of Pediatrics, Hacettepe University Children's Hospital, 06100 Ankara, Turkey
| | - Safak Gucer
- Pathology Unit, Department of Pediatrics, Hacettepe University Children's Hospital, 06100 Ankara, Turkey
| | - Annalisa Botta
- Medical Genetics Section, Department of Biomedicine and Prevention, Tor Vergata University of Rome, 00133 Rome, Italy
| | - Elena Pegoraro
- Neuromuscular Center, Department of Neurosciences, University of Padova, 35129 Padova, Italy
| | - Adriana Malena
- Neuromuscular Center, Department of Neurosciences, University of Padova, 35129 Padova, Italy
| | - Lodovica Vergani
- Neuromuscular Center, Department of Neurosciences, University of Padova, 35129 Padova, Italy
| | - Daniela Mazzà
- Italy Institute of Medical Genetics, Catholic University of Roma, 00168 Rome, Italy
| | - Marcella Zollino
- Italy Institute of Medical Genetics, Catholic University of Roma, 00168 Rome, Italy
| | - Daniele Ghezzi
- Molecular Neurogenetics Unit, Foundation IRCCS Neurological Institute C. Besta, 20126 Milan, Italy
| | - Cecile Acquaviva
- Service Maladies Héréditaires du Métabolisme et Dépistage Néonatal, Centre de Biologie et Pathologie Est, Centre Hospitalier Universitaire Lyon, 69500 Bron, France
| | - Tiina Tyni
- Department of Pediatric Neurology, Hospital for Children and Adolescence, Helsinki University Central Hospital, 280 Helsinki, Finland
| | - Avihu Boneh
- Murdoch Childrens Research Institute and University of Melbourne, Melbourne, VIC 3010, Australia
| | - Thomas Meitinger
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Tim M Strom
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Niels Gregersen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and University Hospital, 8200 Aarhus N, Denmark
| | - Johannes A Mayr
- Department of Paediatrics, Paracelsus Medical University, SALK Salzburg, 5020 Salzburg, Austria
| | - Rita Horvath
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK
| | - Maria Barile
- Department of Biosciences, Biotechnology, and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy.
| | - Holger Prokisch
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| |
Collapse
|
9
|
Fuchs JE, Muñoz IG, Timson DJ, Pey AL. Experimental and computational evidence on conformational fluctuations as a source of catalytic defects in genetic diseases. RSC Adv 2016. [DOI: 10.1039/c6ra05499d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Catalytic mutants causing inherited type III galactosemia alter active site structural dynamics and shift the native conformational equilibrium towards inactive conformations.
Collapse
Affiliation(s)
- Julian E. Fuchs
- Institute of General, Inorganic and Theoretical Chemistry
- Faculty of Chemistry and Pharmacy
- University of Innsbruck
- Innsbruck
- Austria
| | - Inés G. Muñoz
- Crystallography and Protein Engineering Unit
- Structural Biology and Biocomputing Programme
- Spanish National Cancer Research Centre (CNIO)
- Madrid
- Spain
| | - David J. Timson
- School of Pharmacy and Biomolecular Sciences
- The University of Brighton
- Brighton
- UK
| | - Angel L. Pey
- Department of Physical Chemistry
- Faculty of Sciences
- University of Granada
- Granada
- Spain
| |
Collapse
|
10
|
Timson DJ. Value of predictive bioinformatics in inherited metabolic diseases. World J Med Genet 2015; 5:46-51. [DOI: 10.5496/wjmg.v5.i3.46] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 04/28/2015] [Accepted: 05/18/2015] [Indexed: 02/06/2023] Open
Abstract
Typically, inherited metabolic diseases arise from point mutations in genes encoding metabolic enzymes. Although some of these mutations directly affect amino acid residues in the active sites of these enzymes, the majority do not. It is now well accepted that the majority of these disease-associated mutations exert their effects through alteration of protein stability, which causes a reduction in enzymatic activity. This finding suggests a way to predict the severity of newly discovered mutations. In silico prediction of the effects of amino acid sequence alterations on protein stability often correlates with disease severity. However, no stability prediction tool is perfect and, in general, better results are obtained if the predictions from a variety of tools are combined and then interpreted. In addition to predicted alterations to stability, the degree of conservation of a particular residue can also be a factor which needs to be taken into account: alterations to highly conserved residues are more likely to be associated with severe forms of the disease. The approach has been successfully applied in a variety of inherited metabolic diseases, but further improvements are necessary to enable robust translation into clinically useful tools.
Collapse
|
11
|
Ethylmalonic encephalopathy ETHE1 R163W/R163Q mutations alter protein stability and redox properties of the iron centre. PLoS One 2014; 9:e107157. [PMID: 25198162 PMCID: PMC4157841 DOI: 10.1371/journal.pone.0107157] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 08/06/2014] [Indexed: 11/19/2022] Open
Abstract
ETHE1 is an iron-containing protein from the metallo β-lactamase family involved in the mitochondrial sulfide oxidation pathway. Mutations in ETHE1 causing loss of function result in sulfide toxicity and in the rare fatal disease Ethylmalonic Encephalopathy (EE). Frequently mutations resulting in depletion of ETHE1 in patient cells are due to severe structural and folding defects. However, some ETHE1 mutations yield nearly normal protein levels and in these cases disease mechanism was suspected to lie in compromised catalytic activity. To address this issue and to elicit how ETHE1 dysfunction results in EE, we have investigated two such pathological mutations, ETHE1-p.Arg163Gln and p.Arg163Trp. In addition, we report a number of benchmark properties of wild type human ETHE1, including for the first time the redox properties of the mononuclear iron centre. We show that loss of function in these variants results from a combination of decreased protein stability and activity. Although structural assessment revealed that the protein fold is not perturbed by mutations, both variants have decreased thermal stabilities and higher proteolytic susceptibilities. ETHE1 wild type and variants bind 1 ± 0.2 mol iron/protein and no zinc; however, the variants exhibited only ≈ 10% of wild-type catalytically activity. Analysis of the redox properties of ETHE1 mononuclear iron centre revealed that the variants have lowered reduction potentials with respect to that of the wild type. This illustrates how point mutation-induced loss of function may arise via very discrete subtle conformational effects on the protein fold and active site chemistry, without extensive disruption of the protein structure or protein-cofactor association.
Collapse
|
12
|
Rhein VF, Carroll J, He J, Ding S, Fearnley IM, Walker JE. Human METTL20 methylates lysine residues adjacent to the recognition loop of the electron transfer flavoprotein in mitochondria. J Biol Chem 2014; 289:24640-51. [PMID: 25023281 PMCID: PMC4148887 DOI: 10.1074/jbc.m114.580464] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammalian mitochondria, protein methylation is a relatively uncommon post-transcriptional modification, and the extent of the mitochondrial protein methylome, the modifying methyltransferases, and their substrates have been little studied. As shown here, the β-subunit of the electron transfer flavoprotein (ETF) is one such methylated protein. The ETF is a heterodimer of α- and β-subunits. Lysine residues 199 and 202 of mature ETFβ are almost completely trimethylated in bovine heart mitochondria, whereas ETFα is not methylated. The enzyme responsible for the modifications was identified as methyltransferase-like protein 20 (METTL20). In human 143B cells, the methylation of ETFβ is less extensive and is diminished further by suppression of METTL20. Tagged METTL20 expressed in HEK293T cells specifically associates with the ETF and promotes the trimethylation of ETFβ lysine residues 199 and 202. ETF serves as a mobile electron carrier linking dehydrogenases involved in fatty acid oxidation and one-carbon metabolism to the membrane-associated ubiquinone pool. The methylated residues in ETFβ are immediately adjacent to a protein loop that recognizes and binds to the dehydrogenases. Suppression of trimethylation of ETFβ in mouse C2C12 cells oxidizing palmitate as an energy source reduced the consumption of oxygen by the cells. These experiments suggest that the oxidation of fatty acids in mitochondria and the passage of electrons via the ETF may be controlled by modulating the protein-protein interactions between the reduced dehydrogenases and the β-subunit of the ETF by trimethylation of lysine residues. METTL20 is the first lysine methyltransferase to be found to be associated with mitochondria.
Collapse
Affiliation(s)
- Virginie F Rhein
- From The Medical Research Council Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - Joe Carroll
- From The Medical Research Council Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - Jiuya He
- From The Medical Research Council Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - Shujing Ding
- From The Medical Research Council Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - Ian M Fearnley
- From The Medical Research Council Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - John E Walker
- From The Medical Research Council Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| |
Collapse
|
13
|
Valentini G, Maggi M, Pey AL. Protein Stability, Folding and Misfolding in Human PGK1 Deficiency. Biomolecules 2013; 3:1030-52. [PMID: 24970202 PMCID: PMC4030965 DOI: 10.3390/biom3041030] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 12/06/2013] [Accepted: 12/13/2013] [Indexed: 01/08/2023] Open
Abstract
Conformational diseases are often caused by mutations, altering protein folding and stability in vivo. We review here our recent work on the effects of mutations on the human phosphoglycerate kinase 1 (hPGK1), with a particular focus on thermodynamics and kinetics of protein folding and misfolding. Expression analyses and in vitro biophysical studies indicate that disease-causing mutations enhance protein aggregation propensity. We found a strong correlation among protein aggregation propensity, thermodynamic stability, cooperativity and dynamics. Comparison of folding and unfolding properties with previous reports in PGKs from other species suggests that hPGK1 is very sensitive to mutations leading to enhance protein aggregation through changes in protein folding cooperativity and the structure of the relevant denaturation transition state for aggregation. Overall, we provide a mechanistic framework for protein misfolding of hPGK1, which is insightful to develop new therapeutic strategies aimed to target native state stability and foldability in hPGK1 deficient patients.
Collapse
Affiliation(s)
- Giovanna Valentini
- Dipartimento di Biologia e Biotecnologie "L. Spallanzani", Università degli Studi di Pavia, Viale Taramelli, 3B, Pavia 27100, Italy.
| | - Maristella Maggi
- Dipartimento di Biologia e Biotecnologie "L. Spallanzani", Università degli Studi di Pavia, Viale Taramelli, 3B, Pavia 27100, Italy.
| | - Angel L Pey
- Department of Physical Chemistry, Faculty of Science, University of Granada, Av. Fuentenueva s/n, Granada 18071, Spain.
| |
Collapse
|
14
|
Olsen RKJ, Cornelius N, Gregersen N. Genetic and cellular modifiers of oxidative stress: what can we learn from fatty acid oxidation defects? Mol Genet Metab 2013; 110 Suppl:S31-9. [PMID: 24206932 DOI: 10.1016/j.ymgme.2013.10.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 10/08/2013] [Accepted: 10/08/2013] [Indexed: 11/16/2022]
Abstract
During the last two decades the realization has emerged that the phenotype of the majority of inherited genetic diseases, including inborn errors of metabolism, cannot be predicted by the genotype identified in patients. This is true for PKU and in the majority of fatty acid oxidation (FAO) defects, where the genotypes identified in patients may be allocated into two groups. One comprising big deletions and small out-of-frame deletions/insertions as well as severe splice and stop codon changes, generally giving rise to no or very little protein product, and the other group, comprising small in-frame deletions/insertions and missense variations, resulting in misfolding proteins with varying stability. In all cases of FAO defects the pathophysiology may be due to energy insufficiency as well as toxic effects from accumulated enzyme substrates. In patients carrying missense variations, it may in addition be caused by the presence of misfolding proteins. A common effect of accumulated substrates and misfolding proteins is chronic oxidative stress, the severeness of which may depend on a complex interplay of modifying factors, including genetic, cellular, environmental and dietary. In this review we will discuss the hypothesis that especially the amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS), created in connection with the electron transport chain (ETC), are the driving forces in the balance between cell survival and death. In young and healthy cells small amounts of ROS function as signaling molecules, activating cell protection systems, such as protein quality networks, antioxidant enzymes and metabolic shift from ATP production by the ETC to glycolysis. In the sick and old cell, containing misfolding and damaged proteins, the dynamic range of these protecting systems are narrowed, and cells develop a state of chronic stress, which easier than young and healthy cells may initiate cell death programs like apoptosis and necrosis. We will discuss a wealth of literature that support this hypothesis, which - if supported by studies - is important for new treatment strategies. We conclude that crude antioxidant treatment may not be beneficial, since it may inhibit the survival stress responses. We discuss the ongoing studies to enhance the residual activity of mild misfolding enzyme proteins by cofactor or chemical chaperones or by inducing the transcription of FAO enzyme proteins by bezafibrate with respect to misfolding/distorted conformational proteins ability to create ROS, and the need to know the exact pathophysiological mechanisms in order to suggest new treatment regimes.
Collapse
Affiliation(s)
- Rikke Katrine Jentoft Olsen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Brendstrupgaardsvej 100, Aarhus, Denmark.
| | | | | |
Collapse
|
15
|
Rodrigues JV, Gomes CM. Mechanism of superoxide and hydrogen peroxide generation by human electron-transfer flavoprotein and pathological variants. Free Radic Biol Med 2012; 53:12-9. [PMID: 22588007 DOI: 10.1016/j.freeradbiomed.2012.04.016] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 04/10/2012] [Accepted: 04/12/2012] [Indexed: 11/26/2022]
Abstract
Reactive oxygen species production by mitochondrial enzymes plays a fundamental role both in cellular signaling and in the progression of dysfunctional states. However, sources of reactive oxygen species and the mechanisms by which enzymes produce these reactive species still remain elusive. We characterized the generation of reactive oxygen species by purified human electron-transfer flavoprotein (ETF), a mitochondrial enzyme that has a central role in the metabolism of lipids, amino acids, and choline. The results showed that ETF produces significant amounts of both superoxide and hydrogen peroxide in the presence of its partner enzyme medium-chain acyl-CoA dehydrogenase (MCAD). ETF-mediated production of reactive oxygen species is partially inhibited at high MCAD/ETF ratios, whereas it is enhanced at high ionic strength. Determination of the reduction potentials of ETF showed that thermodynamic properties of the FAD cofactor are changed upon formation of a complex between ETF and MCAD, supporting the notion that protein:protein interactions modulate the reactivity of the protein with dioxygen. Two pathogenic ETF variants were also studied to determine which factors modulate the reactivity toward molecular oxygen and promote reactive oxygen species production. The results obtained show that destabilized conformations and defective protein:protein interactions increase the ability of ETF to generate reactive oxygen species. A possible role for these processes in mitochondrial dysfunction in metabolic disorders of fatty acid β-oxidation is discussed.
Collapse
Affiliation(s)
- João V Rodrigues
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal
| | | |
Collapse
|
16
|
Alves E, Henriques BJ, Rodrigues JV, Prudêncio P, Rocha H, Vilarinho L, Martinho RG, Gomes CM. Mutations at the flavin binding site of ETF:QO yield a MADD-like severe phenotype in Drosophila. Biochim Biophys Acta Mol Basis Dis 2012; 1822:1284-92. [PMID: 22580358 DOI: 10.1016/j.bbadis.2012.05.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 05/03/2012] [Accepted: 05/04/2012] [Indexed: 11/30/2022]
Abstract
Following a screening on EMS-induced Drosophila mutants defective for formation and morphogenesis of epithelial cells, we have identified three lethal mutants defective for the production of embryonic cuticle. The mutants are allelic to the CG12140 gene, the fly homologue of electron transfer flavoprotein:ubiquinone oxidoreductase (ETF:QO). In humans, inherited defects in this inner membrane protein account for multiple acyl-CoA dehydrogenase deficiency (MADD), a metabolic disease of β-oxidation, with a broad range of clinical phenotypes, varying from embryonic lethal to mild forms. The three mutant alleles carried distinct missense mutations in ETF:QO (G65E, A68V and S104F) and maternal mutant embryos for ETF:QO showed lethal morphogenetic defects and a significant induction of apoptosis following germ-band elongation. This phenotype is accompanied by an embryonic accumulation of short- and medium-chain acylcarnitines (C4, C8 and C12) as well as long-chain acylcarnitines (C14 and C16:1), whose elevation is also found in severe MADD forms in humans under intense metabolic decompensation. In agreement the ETF:QO activity in the mutant embryos is markedly decreased in relation to wild type activity. Amino acid sequence analysis and structural mapping into a molecular model of ETF:QO show that all mutations map at FAD interacting residues, two of which at the nucleotide-binding Rossmann fold. This structural domain is composed by a β-strand connected by a short loop to an α-helix, and its perturbation results in impaired cofactor association via structural destabilisation and consequently enzymatic inactivation. This work thus pinpoints the molecular origins of a severe MADD-like phenotype in the fruit fly and establishes the proof of concept concerning the suitability of this organism as a potential model organism for MADD.
Collapse
Affiliation(s)
- Ema Alves
- Instituto Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Analyzing effects of naturally occurring missense mutations. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2012; 2012:805827. [PMID: 22577471 PMCID: PMC3346971 DOI: 10.1155/2012/805827] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 02/01/2012] [Accepted: 02/01/2012] [Indexed: 11/17/2022]
Abstract
Single-point mutation in genome, for example, single-nucleotide polymorphism (SNP) or rare genetic mutation, is the change of a single nucleotide for another in the genome sequence. Some of them will produce an amino acid substitution in the corresponding protein sequence (missense mutations); others will not. This paper focuses on genetic mutations resulting in a change in the amino acid sequence of the corresponding protein and how to assess their effects on protein wild-type characteristics. The existing methods and approaches for predicting the effects of mutation on protein stability, structure, and dynamics are outlined and discussed with respect to their underlying principles. Available resources, either as stand-alone applications or webservers, are pointed out as well. It is emphasized that understanding the molecular mechanisms behind these effects due to these missense mutations is of critical importance for detecting disease-causing mutations. The paper provides several examples of the application of 3D structure-based methods to model the effects of protein stability and protein-protein interactions caused by missense mutations as well.
Collapse
|