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Foroutannejad S, Good LL, Lin C, Carter ZI, Tadesse MG, Lucius AL, Crane BR, Maillard RA. The cofactor-dependent folding mechanism of Drosophila cryptochrome revealed by single-molecule pulling experiments. Nat Commun 2023; 14:1057. [PMID: 36828841 PMCID: PMC9958137 DOI: 10.1038/s41467-023-36701-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 02/10/2023] [Indexed: 02/26/2023] Open
Abstract
The link between cofactor binding and protein activity is well-established. However, how cofactor interactions modulate folding of large proteins remains unknown. We use optical tweezers, clustering and global fitting to dissect the folding mechanism of Drosophila cryptochrome (dCRY), a 542-residue protein that binds FAD, one of the most chemically and structurally complex cofactors in nature. We show that the first dCRY parts to fold are independent of FAD, but later steps are FAD-driven as the remaining polypeptide folds around the cofactor. FAD binds to largely unfolded intermediates, yet with association kinetics above the diffusion-limit. Interestingly, not all FAD moieties are required for folding: whereas the isoalloxazine ring linked to ribitol and one phosphate is sufficient to drive complete folding, the adenosine ring with phosphates only leads to partial folding. Lastly, we propose a dCRY folding model where regions that undergo conformational transitions during signal transduction are the last to fold.
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Affiliation(s)
| | - Lydia L Good
- Department of Chemistry, Georgetown University, Washington, DC, USA
| | - Changfan Lin
- Department of Chemistry & Chemical Biology, Cornell University, Ithaca, NY, USA
| | - Zachariah I Carter
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Mahlet G Tadesse
- Department of Mathematics and Statistics, Georgetown University, Washington, DC, USA
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Brian R Crane
- Department of Chemistry & Chemical Biology, Cornell University, Ithaca, NY, USA
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2
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ETF-QO Mutants Uncoupled Fatty Acid β-Oxidation and Mitochondrial Bioenergetics Leading to Lipid Pathology. Cells 2019; 8:cells8020106. [PMID: 30709034 PMCID: PMC6406559 DOI: 10.3390/cells8020106] [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: 12/11/2018] [Revised: 01/24/2019] [Accepted: 01/28/2019] [Indexed: 12/13/2022] Open
Abstract
The electron-transfer flavoprotein dehydrogenase gene (ETFDH) that encodes the ETF-ubiquinone oxidoreductase (ETF-QO) has been reported to be the major cause of multiple acyl-CoA dehydrogenase deficiency (MADD). ETF-QO is an electron carrier that mainly functions in mitochondrial fatty acid β-oxidation and the delivery of electrons to the ubiquinone pool in the mitochondrial respiratory chain. A high frequency of c.250G>A has been found in Taiwanese patients with late-onset MADD. We postulated that the ETFDH c.250G>A mutation may concomitantly impair fatty acid β-oxidation and mitochondrial function. Using MADD patient-derived lymphoblastoid cells and specifically overexpressed ETFDH c.92C>T, c.250G>A, or coexisted c.92C>T and c.250G>A (c.92C>T + c.250G>A) mutated lymphoblastoid cells, we addressed the genotype-phenotype relationship of ETFDH variation in the pathogenesis of MADD. The decreased adenosine triphosphate synthesis, dissipated mitochondrial membrane potentials, reduced mitochondrial bioenergetics, and increased neutral lipid droplets and lipid peroxides were found in the MADD patient-derived lymphoblastoid cells. Riboflavin and/or coenzyme Q10 supplementation rescued cells from lipid droplet accumulation. All three mutant types, c.92C>T, c.250G>A, or c.92C>T + c.250G>A, had increased lipid droplet accumulation after treatment with palmitic acid. These results help to clarify the molecular pathogenesis of MADD as a result of the high frequency of the ETFDH c.250G>A and c.92C>T mutations.
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Xu J, Li D, Lv J, Xu X, Wen B, Lin P, Liu F, Ji K, Shan J, Li H, Li W, Zhao Y, Zhao D, Pok JY, Yan C. ETFDH Mutations and Flavin Adenine Dinucleotide Homeostasis Disturbance Are Essential for Developing Riboflavin-Responsive Multiple Acyl-Coenzyme A Dehydrogenation Deficiency. Ann Neurol 2018; 84:659-673. [PMID: 30232818 DOI: 10.1002/ana.25338] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Revised: 08/26/2018] [Accepted: 09/09/2018] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Riboflavin-responsive multiple acyl-coenzyme A dehydrogenation deficiency (RR-MADD) is an inherited fatty acid metabolism disorder mainly caused by genetic defects in electron transfer flavoprotein-ubiquinone oxidoreductase (ETF:QO). The variant ETF:QO protein folding deficiency, which can be corrected by therapeutic dosage of riboflavin supplement, has been identified in HEK-293 cells and is believed to be the molecular mechanism of this disease. To verify this hypothesis in vivo, we generated Etfdh (h)A84T knockin (KI) mice. METHODS Tissues from these mice as well as muscle biopsies and fibroblasts from 7 RR-MADD patients were used to examine the flavin adenine dinucleotide (FAD) concentration and ETF:QO protein amount. RESULTS All of the homozygous KI mice (Etfdh (h)A84T/(h)A84T , KI/KI) were initially normal. After being given a high-fat and vitamin B2 -deficient (HF-B2 D) diet for 5 weeks, they developed weight loss, movement ability defects, lipid storage in muscle and liver, and elevated serum acyl-carnitine levels, which are clinically and biochemically similar to RR-MADD patients. Both ETF:QO protein and FAD concentrations were significantly decreased in tissues of HF-B2 D-KI/KI mice and in cultured fibroblasts from RR-MADD patients. After riboflavin treatment, ETF:QO protein increased in proportion to elevated FAD concentrations, but not related to mRNA levels. These results were further confirmed in cultured fibroblasts from RR-MADD patients. INTERPRETATION For the first time, we successfully developed a RR-MADD mice model and confirmed that FAD homeostasis disturbances played a crucial role on the pathomechanism of RR-MADD in this mouse model and culture cells from patients. Supplementation of riboflavin may stabilize variant ETF:QO protein by rebuilding FAD homeostasis. Ann Neurol 2018;84:667-681.
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Affiliation(s)
- Jingwen Xu
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Duoling Li
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Jingwei Lv
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Xuebi Xu
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Bing Wen
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Pengfei Lin
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Fuchen Liu
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China.,Department of Neurobiology, Yale University School of Medicine, New Haven, CT
| | - Kunqian Ji
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Jingli Shan
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Honghao Li
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Wei Li
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Yuying Zhao
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Dandan Zhao
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Joo Y Pok
- Department of Neurology, Yale University, New Haven, CT
| | - Chuanzhu Yan
- Research Institute of Neuromuscular and Neurodegenerative Disease, Department of Neurology, Qilu Hospital, Shandong University, Jinan, China.,Brain Science Research Institute, Shandong University, Jinan, China.,Laboratory of Mitochondrial Medicine, Qilu Hospital (Qingdao), Qingdao, China
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4
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Houwman JA, van Mierlo CPM. Folding of proteins with a flavodoxin-like architecture. FEBS J 2017; 284:3145-3167. [PMID: 28380286 DOI: 10.1111/febs.14077] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/13/2017] [Accepted: 04/03/2017] [Indexed: 12/21/2022]
Abstract
The flavodoxin-like fold is a protein architecture that can be traced back to the universal ancestor of the three kingdoms of life. Many proteins share this α-β parallel topology and hence it is highly relevant to illuminate how they fold. Here, we review experiments and simulations concerning the folding of flavodoxins and CheY-like proteins, which share the flavodoxin-like fold. These polypeptides tend to temporarily misfold during unassisted folding to their functionally active forms. This susceptibility to frustration is caused by the more rapid formation of an α-helix compared to a β-sheet, particularly when a parallel β-sheet is involved. As a result, flavodoxin-like proteins form intermediates that are off-pathway to native protein and several of these species are molten globules (MGs). Experiments suggest that the off-pathway species are of helical nature and that flavodoxin-like proteins have a nonconserved transition state that determines the rate of productive folding. Folding of flavodoxin from Azotobacter vinelandii has been investigated extensively, enabling a schematic construction of its folding energy landscape. It is the only flavodoxin-like protein of which cotranslational folding has been probed. New insights that emphasize differences between in vivo and in vitro folding energy landscapes are emerging: the ribosome modulates MG formation in nascent apoflavodoxin and forces this polypeptide toward the native state.
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Affiliation(s)
- Joseline A Houwman
- Laboratory of Biochemistry, Wageningen University and Research, The Netherlands
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5
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Liu XY, Wang ZQ, Wang DN, Lin MT, Wang N. A Historical Cohort Study on the Efficacy of Glucocorticoids and Riboflavin Among Patients with Late-onset Multiple Acyl-CoA Dehydrogenase Deficiency. Chin Med J (Engl) 2017; 129:142-6. [PMID: 26830983 PMCID: PMC4799539 DOI: 10.4103/0366-6999.173438] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Background: Late-onset multiple acyl-CoA dehydrogenase deficiency (MADD) is the most common type of lipid storage myopathies in China. Most patients with late-onset MADD are well responsive to riboflavin. Up to now, these patients are often treated with glucocorticoids as the first-line drug because they are misdiagnosed as polymyositis without muscle biopsy or gene analysis. Although glucocorticoids seem to improve the fatty acid metabolism of late-onset MADD, the objective evaluation of their rationalization on this disorder and comparison with riboflavin treatment are unknown. Methods: We performed a historical cohort study on the efficacy of the two drugs among 45 patients with late-onset MADD, who were divided into glucocorticoids group and riboflavin group. Detailed clinical information of baseline and 1-month follow-up were collected. Results: After 1-month treatment, a dramatic improvement of muscle strength was found in riboflavin group (P < 0.05). There was no significant difference in muscle enzymes between the two groups. Significantly, the number of patients with full recovery in glucocorticoids group was less than the number in riboflavin group (P < 0.05). On the other hand, almost half of the patients in riboflavin group still presented high-level muscle enzymes and weak muscle strength after 1-month riboflavin treatment, meaning that 1-month treatment duration maybe insufficient and patients should keep on riboflavin supplement for a longer time. Conclusions: Our results provide credible evidences that the overall efficacy of riboflavin is superior to glucocorticoids, and a longer duration of riboflavin treatment is necessary for patients with late-onset MADD.
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Affiliation(s)
| | | | | | | | - Ning Wang
- Department of Neurology and Institute of Neurology, First Affiliated Hospital, Fujian Medical University; Fujian Key Laboratory of Molecular Neurology, Fuzhou, Fujian 350005, China
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Xi J, Wen B, Lin J, Zhu W, Luo S, Zhao C, Li D, Lin P, Lu J, Yan C. Clinical features and ETFDH mutation spectrum in a cohort of 90 Chinese patients with late-onset multiple acyl-CoA dehydrogenase deficiency. J Inherit Metab Dis 2014; 37:399-404. [PMID: 24357026 DOI: 10.1007/s10545-013-9671-6] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 12/03/2013] [Accepted: 12/05/2013] [Indexed: 12/13/2022]
Abstract
The major cause of lipid storage myopathies (LSM) in China is multiple acyl-CoA dehydrogenase deficiency (MADD) caused by ETFDH mutations. We here present an analysis of the spectrum of ETFDH mutations in the largest cohort of patients with MADD (90 unrelated patients). We identified 61 ETFDH mutations, including 31 novel mutations, which were widely distributed within the coding sequence. Three frequent mutations were identified: c.250G > A (most common in South China), c.770A > G and c.1227A > C (most common in both South and North China). Regional differences of allele frequency and further haplotype analysis suggest the possibility of founder effects of c.250G > A and c.770A > G. These findings promise to provide the basis for implementing a rapid and economical strategy for diagnosing MADD.
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Affiliation(s)
- Jianying Xi
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
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The chaperone role of the pyridoxal 5′-phosphate and its implications for rare diseases involving B6-dependent enzymes. Clin Biochem 2014; 47:158-65. [DOI: 10.1016/j.clinbiochem.2013.11.021] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 11/28/2013] [Accepted: 11/30/2013] [Indexed: 02/06/2023]
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Laser temperature-jump spectroscopy of intrinsically disordered proteins. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2012; 896:267-81. [PMID: 22821531 DOI: 10.1007/978-1-4614-3704-8_18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
Laser temperature-jump methods allow an experimenter to study the kinetics and dynamics of very rapid solution-phase processes, including conformational dynamics of biomolecules on time scales of nanoseconds and microseconds. The combination of laser temperature-jump (T-jump) excitation and appropriate optical detection techniques such as fluorescence energy transfer allows the study of intramolecular and intermolecular conformational changes and interactions that occur during protein folding and binding. This article describes the application of the laser temperature-jump method to UV-visible fluorescence studies of the coupled folding and binding of intrinsically disordered proteins. We emphasize the practical aspects of instrument alignment and optimization, sample preparation, and data collection using fluorescently labeled peptides with UV laser excitation.
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9
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Chen J. Towards the physical basis of how intrinsic disorder mediates protein function. Arch Biochem Biophys 2012; 524:123-31. [PMID: 22579883 DOI: 10.1016/j.abb.2012.04.024] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 04/28/2012] [Accepted: 04/30/2012] [Indexed: 02/06/2023]
Abstract
Intrinsically disordered proteins (IDPs) are an important class of functional proteins that is highly prevalent in biology and has broad association with human diseases. In contrast to structured proteins, free IDPs exist as heterogeneous and dynamical conformational ensembles under physiological conditions. Many concepts have been discussed on how such intrinsic disorder may provide crucial functional advantages, particularly in cellular signaling and regulation. Establishing the physical basis of these proposed phenomena requires not only detailed characterization of the disordered conformational ensembles, but also mechanistic understanding of the roles of various ensemble properties in IDP interaction and regulation. Here, we review the experimental and computational approaches that may be integrated to address many important challenges of establishing a "structural" basis of IDP function, and discuss some of the key emerging ideas on how the conformational ensembles of IDPs may mediate function, especially in coupled binding and folding interactions.
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Affiliation(s)
- Jianhan Chen
- Department of Biochemistry, Kansas State University, Manhattan, KS 66506, USA.
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10
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Papadakos G, Housden NG, Lilly KJ, Kaminska R, Kleanthous C. Kinetic Basis for the Competitive Recruitment of TolB by the Intrinsically Disordered Translocation Domain of Colicin E9. J Mol Biol 2012; 418:269-80. [DOI: 10.1016/j.jmb.2012.01.039] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 01/11/2012] [Accepted: 01/24/2012] [Indexed: 11/15/2022]
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11
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Er TK, Chen CC, Liu YY, Chang HC, Chien YH, Chang JG, Hwang JK, Jong YJ. Computational analysis of a novel mutation in ETFDH gene highlights its long-range effects on the FAD-binding motif. BMC STRUCTURAL BIOLOGY 2011; 11:43. [PMID: 22013910 PMCID: PMC3209457 DOI: 10.1186/1472-6807-11-43] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 10/21/2011] [Indexed: 11/10/2022]
Abstract
Background Multiple acyl-coenzyme A dehydrogenase deficiency (MADD) is an autosomal recessive disease caused by the defects in the mitochondrial electron transfer system and the metabolism of fatty acids. Recently, mutations in electron transfer flavoprotein dehydrogenase (ETFDH) gene, encoding electron transfer flavoprotein:ubiquinone oxidoreductase (ETF:QO) have been reported to be the major causes of riboflavin-responsive MADD. To date, no studies have been performed to explore the functional impact of these mutations or their mechanism of disrupting enzyme activity. Results High resolution melting (HRM) analysis and sequencing of the entire ETFDH gene revealed a novel mutation (p.Phe128Ser) and the hotspot mutation (p.Ala84Thr) from a patient with MADD. According to the predicted 3D structure of ETF:QO, the two mutations are located within the flavin adenine dinucleotide (FAD) binding domain; however, the two residues do not have direct interactions with the FAD ligand. Using molecular dynamics (MD) simulations and normal mode analysis (NMA), we found that the p.Ala84Thr and p.Phe128Ser mutations are most likely to alter the protein structure near the FAD binding site as well as disrupt the stability of the FAD binding required for the activation of ETF:QO. Intriguingly, NMA revealed that several reported disease-causing mutations in the ETF:QO protein show highly correlated motions with the FAD-binding site. Conclusions Based on the present findings, we conclude that the changes made to the amino acids in ETF:QO are likely to influence the FAD-binding stability.
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Affiliation(s)
- Tze-Kiong Er
- Division of Molecular Diagnostics, Department of Laboratory Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Taiwan
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12
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Molecular analysis of 51 unrelated pedigrees with late-onset multiple acyl-CoA dehydrogenation deficiency (MADD) in southern China confirmed the most common ETFDH mutation and high carrier frequency of c.250G>A. J Mol Med (Berl) 2011; 89:569-76. [PMID: 21347544 DOI: 10.1007/s00109-011-0725-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 12/12/2010] [Accepted: 12/14/2010] [Indexed: 10/18/2022]
Abstract
Multiple acyl-CoA dehydrogenation deficiency (MADD) is an autosomal recessive disease affecting amino acid, fatty acid, and choline metabolisms and is a common genetic defect responsible for lipid storage myopathy. Most forms of MADD are caused by a deficiency of electron transfer flavoprotein (ETF) or ETF dehydrogenase (ETFDH). However, its molecular feature has not been found uniformly in previous reports of Chinese patients. A large cohort of 56 late-onset MADD patients from 51 unrelated pedigrees in southern China was recruited to investigate a clear correlation between clinical phenotype and molecular genetic basis. All exons of ETFA, ETFB, and ETFDH, including the intron-exon boundaries, and 5' and 3' untranslated regions were directly sequenced. ETFDH deficiencies affected 94.1% (48/51) of the pedigrees. ETFDH-c.250G>A is the most common mutation, representing a high allelic frequency of 83.3% (80/96). Carrier frequency of c.250G>A is estimated to be 1.35% (7/520) in the normal population. A significant reduced expression of ETFDH was identified in the muscle of ETFDH-deficient patients. ETFDH deficiency is a major cause of riboflavin-responsive MADD in southern China, and c.250G>A is an important mutation that could be employed as a fast and reliable screening method.
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Stagg L, Christiansen A, Wittung-Stafshede P. Macromolecular crowding tunes folding landscape of parallel α/β protein, apoflavodoxin. J Am Chem Soc 2010; 133:646-8. [PMID: 21175168 DOI: 10.1021/ja107638e] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proteins normally fold in crowded cellular environments. Here we use a set of Desulfovibrio desulfuricans apoflavodoxin variants to assess--with residue-specific resolution--how apoflavodoxin's folding landscape is tuned by macromolecular crowding. We find that, under crowded conditions, initial topological frustration is reduced, subsequent folding requires less ordering in the transition state, and β-strand 1 becomes more important in guiding the process. We propose that conditions more closely mimicking the cellular environment make the ensemble of unfolded conformations less expanded, resulting in a folding funnel that is smoother and narrower.
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Affiliation(s)
- Loren Stagg
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, United States
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14
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Stagg L, Samiotakis A, Homouz D, Cheung MS, Wittung-Stafshede P. Residue-specific analysis of frustration in the folding landscape of repeat beta/alpha protein apoflavodoxin. J Mol Biol 2009; 396:75-89. [PMID: 19913555 DOI: 10.1016/j.jmb.2009.11.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Revised: 11/04/2009] [Accepted: 11/05/2009] [Indexed: 11/17/2022]
Abstract
Flavodoxin adopts the common repeat beta/alpha topology and folds in a complex kinetic reaction with intermediates. To better understand this reaction, we analyzed a set of Desulfovibrio desulfuricans apoflavodoxin variants with point mutations in most secondary structure elements by in vitro and in silico methods. By equilibrium unfolding experiments, we first revealed how different secondary structure elements contribute to overall protein resistance to heat and urea. Next, using stopped-flow mixing coupled with far-UV circular dichroism, we probed how individual residues affect the amount of structure formed in the experimentally detected burst-phase intermediate. Together with in silico folding route analysis of the same point-mutated variants and computation of growth in nucleation size during early folding, computer simulations suggested the presence of two competing folding nuclei at opposite sides of the central beta-strand 3 (i.e., at beta-strands 1 and 4), which cause early topological frustration (i.e., misfolding) in the folding landscape. Particularly, the extent of heterogeneity in folding nuclei growth correlates with the in vitro burst-phase circular dichroism amplitude. In addition, phi-value analysis (in vitro and in silico) of the overall folding barrier to apoflavodoxin's native state revealed that native-like interactions in most of the beta-strands must form in transition state. Our study reveals that an imbalanced competition between the two sides of apoflavodoxin's central beta-sheet directs initial misfolding, while proper alignment on both sides of beta-strand 3 is necessary for productive folding.
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Affiliation(s)
- Loren Stagg
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251, USA
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15
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Kinetic advantage of intrinsically disordered proteins in coupled folding-binding process: a critical assessment of the "fly-casting" mechanism. J Mol Biol 2009; 393:1143-59. [PMID: 19747922 DOI: 10.1016/j.jmb.2009.09.010] [Citation(s) in RCA: 212] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 06/29/2009] [Accepted: 09/04/2009] [Indexed: 11/20/2022]
Abstract
Intrinsically disordered proteins (IDPs) are recognized to play important roles in many biological functions such as transcription and translation regulation, cellular signal transduction, protein phosphorylation, and molecular assemblies. The coupling of folding with binding through a "fly-casting" mechanism has been proposed to account for the fast binding kinetics of IDPs. In this article, experimental data from the literature were collated to verify the kinetic advantages of IDPs, while molecular simulations were performed to clarify the origin of the kinetic advantages. The phosphorylated KID-kinase-inducible domain interacting domain (KIX) complex was used as an example in the simulations. By modifying a coarse-grained model with a native-centric Gō-like potential, we were able to continuously tune the degree of disorder of the phosphorylated KID domain and thus investigate the intrinsic role of chain flexibility in binding kinetics. The simulations show that the "fly-casting" effect is not only due to the greater capture radii of IDPs. The coupling of folding with binding of IDPs leads to a significant reduction in binding free-energy barrier. Such a reduction accelerates the binding process. Although the greater capture radius has been regarded as the main factor in promoting the binding rate of IDPs, we found that this parameter will also lead to the slower translational diffusion of IDPs when compared with ordered proteins. As a result, the capture rate of IDPs was found to be slower than that of ordered proteins. The main origin of the faster binding for IDPs are the fewer encounter times required before the formation of the final binding complex. The roles of the interchain native contacts fraction (Q(b)) and the mass-center distance (DeltaR) as reaction coordinates are also discussed.
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Conformational selection or induced fit: a flux description of reaction mechanism. Proc Natl Acad Sci U S A 2009; 106:13737-41. [PMID: 19666553 DOI: 10.1073/pnas.0907195106] [Citation(s) in RCA: 431] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mechanism of ligand binding coupled to conformational changes in macromolecules has recently attracted considerable interest. The 2 limiting cases are the "induced fit" mechanism (binding first) or "conformational selection" (conformational change first). Described here are the criteria by which the sequence of events can be determined quantitatively. The relative importance of the 2 pathways is determined not by comparing rate constants (a common misconception) but instead by comparing the flux through each pathway. The simple rules for calculating flux in multistep mechanisms are described and then applied to 2 examples from the literature, neither of which has previously been analyzed using the concept of flux. The first example is the mechanism of conformational change in the binding of NADPH to dihydrofolate reductase. The second example is the mechanism of flavodoxin folding coupled to binding of its cofactor, flavin mononucleotide. In both cases, the mechanism switches from being dominated by the conformational selection pathway at low ligand concentration to induced fit at high ligand concentration. Over a wide range of conditions, a significant fraction of the flux occurs through both pathways. Such a mixed mechanism likely will be discovered for many cases of coupled conformational change and ligand binding when kinetic data are analyzed by using a flux-based approach.
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Narayanan R, Ganesh OK, Edison AS, Hagen SJ. Kinetics of Folding and Binding of an Intrinsically Disordered Protein: The Inhibitor of Yeast Aspartic Proteinase YPrA. J Am Chem Soc 2008; 130:11477-85. [DOI: 10.1021/ja803221c] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ranjani Narayanan
- Physics Department and Department of Biochemistry and Molecular Biology, University of Florida, P.O. Box 118440, Gainesville FL 32611-8440
| | - Omjoy K. Ganesh
- Physics Department and Department of Biochemistry and Molecular Biology, University of Florida, P.O. Box 118440, Gainesville FL 32611-8440
| | - Arthur S. Edison
- Physics Department and Department of Biochemistry and Molecular Biology, University of Florida, P.O. Box 118440, Gainesville FL 32611-8440
| | - Stephen J. Hagen
- Physics Department and Department of Biochemistry and Molecular Biology, University of Florida, P.O. Box 118440, Gainesville FL 32611-8440
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Molecular crowding enhances native structure and stability of alpha/beta protein flavodoxin. Proc Natl Acad Sci U S A 2007; 104:18976-81. [PMID: 18024596 DOI: 10.1073/pnas.0705127104] [Citation(s) in RCA: 215] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To investigate the consequences of macromolecular crowding on the behavior of a globular protein, we performed a combined experimental and computational study on the 148-residue single-domain alpha/beta protein, Desulfovibrio desulfuricans apoflavodoxin. In vitro thermal unfolding experiments, as well as assessment of native and denatured structures, were probed by using far-UV CD in the presence of various amounts of Ficoll 70, an inert spherical crowding agent. Ficoll 70 has a concentration-dependent effect on the thermal stability of apoflavodoxin (DeltaT(m) of 20 degrees C at 400 mg/ml; pH 7). As judged by CD, addition of Ficoll 70 causes an increase in the amount of secondary structure in the native-state ensemble (pH 7, 20 degrees C) but only minor effects on the denatured state. Theoretical calculations, based on an off-lattice model and hard-sphere particles, are in good agreement with the in vitro data. The simulations demonstrate that, in the presence of 25% volume occupancy of spheres, native flavodoxin is thermally stabilized, and the free energy landscape shifts to favor more compact structures in both native and denatured states. The difference contact map reveals that the native-state compaction originates in stronger interactions between the helices and the central beta-sheet, as well as by less fraying in the terminal helices. This study demonstrates that macromolecular crowding has structural effects on the folded ensemble of polypeptides.
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Deu E, Kirsch JF. Cofactor-Directed Reversible Denaturation Pathways: The Cofactor-Stabilized Escherichia coli Aspartate Aminotransferase Homodimer Unfolds through a Pathway That Differs from That of the Apoenzyme. Biochemistry 2007; 46:5819-29. [PMID: 17441730 DOI: 10.1021/bi602632d] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
While the urea-mediated unfolding pathway of the Escherichia coli aspartate aminotransferase (eAATase) homodimer proceeds through a reversible three-state process with a partially folded dimeric intermediate, D D* 2U (E. Deu and J. F. Kirsch, accompanying paper), that of a cofactor-stabilized form differs. Pyridoxal phosphate, which binds at the intersubunit active sites, stabilizes the native form by 6 kcal mol-1 and dissociates during the D <==> D* transition. Reductive trapping of the cofactor to a nondissociable derivative (PPL-eAATase) precludes the formation of D*. A novel monomeric intermediate (M'-PPL) with 70% of the native secondary structure (circular dichroism) was identified in the unfolding pathway of PPL-eAATase: D-PPL2 <==> 2M'-PPL <==> 2U-PPL. The combined results define two structural regions with distinct stabilities: the active site region (ASR) and the generally more stable, dimerization region (DMR). The DMR includes the key intersubunit contacts. It is responsible for the multimeric nature of D*, and its disorder leads to dimer dissociation. Selective strengthening of the ASR-cofactor interactions by cofactor trapping reverses the relative stabilities of the two regions (from DMR > ASR in the apoenzyme to ASR > DMR in PPL-eAATase) and results in a reordering of the eAATase denaturation pathway.
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Affiliation(s)
- Edgar Deu
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720-3206, USA
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