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Hnízda A, Majtan T, Liu L, Pey AL, Carpenter JF, Kodíček M, Kožich V, Kraus JP. Conformational properties of nine purified cystathionine β-synthase mutants. Biochemistry 2012; 51:4755-63. [PMID: 22612060 PMCID: PMC3384745 DOI: 10.1021/bi300435e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein misfolding due to missense mutations is a common pathogenic mechanism in cystathionine β-synthase (CBS) deficiency. In our previous studies, we successfully expressed, purified, and characterized nine CBS mutant enzymes containing the following patient mutations: P49L, P78R, A114V, R125Q, E176K, R266K, P422L, I435T, and S466L. These purified mutants exhibited full heme saturation, normal tetrameric assembly, and high catalytic activity. In this work, we used several spectroscopic and proteolytic techniques to provide a more thorough insight into the conformation of these mutant enzymes. Far-UV circular dichroism, fluorescence, and second-derivative UV spectroscopy revealed that the spatial arrangement of these CBS mutants is similar to that of the wild type, although the microenvironment of the chromophores may be slightly altered. Using proteolysis with thermolysin under native conditions, we found that the majority of the studied mutants is more susceptible to cleavage, suggesting their increased local flexibility or propensity for local unfolding. Interestingly, the presence of the CBS allosteric activator, S-adenosylmethionine (AdoMet), increased the rate of cleavage of the wild type and the AdoMet-responsive mutants, while the proteolytic rate of the AdoMet-unresponsive mutants was not significantly changed. Pulse proteolysis analysis suggested that the protein structure of the R125Q and E176K mutants is significantly less stable than that of the wild type and the other mutants. Taken together, the proteolytic data shows that the conformation of the pathogenic mutants is altered despite retained catalytic activity and normal tetrameric assembly. This study demonstrates that the proteolytic techniques are useful tools for the assessment of the biochemical penalty of missense mutations in CBS.
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Affiliation(s)
- Aleš Hnízda
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Ke Karlovu 2, 128 08 Prague 2, Czech Republic
| | - Tomas Majtan
- Department of Pediatrics and the Colorado Intellectual and Developmental Disabilities Research Center (IDDRC), University of Colorado at Denver, 12800 E 19th Ave, Aurora, Colorado 80045, USA
- Department of Genomics & Biotechnology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, 84551, Slovakia
| | - Lu Liu
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado at Denver, Aurora, Colorado 80045, USA
| | - Angel L. Pey
- Department of Physical Chemistry, Faculty of Sciences, University of Granada, Granada 18071, Spain
| | - John F. Carpenter
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado at Denver, Aurora, Colorado 80045, USA
| | - Milan Kodíček
- Department of Biochemistry and Microbiology, Institute of Chemical Technology in Prague, Technická 5, 166 28, Prague 6, Czech Republic
| | - Viktor Kožich
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Ke Karlovu 2, 128 08 Prague 2, Czech Republic
| | - Jan P. Kraus
- Department of Pediatrics and the Colorado Intellectual and Developmental Disabilities Research Center (IDDRC), University of Colorado at Denver, 12800 E 19th Ave, Aurora, Colorado 80045, USA
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Janošík M, Sokolová J, Janošíková B, Krijt J, Klatovská V, Kožich V. Birth prevalence of homocystinuria in Central Europe: frequency and pathogenicity of mutation c.1105C>T (p.R369C) in the cystathionine beta-synthase gene. J Pediatr 2009; 154:431-7. [PMID: 18950795 PMCID: PMC2653617 DOI: 10.1016/j.jpeds.2008.09.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 08/11/2008] [Accepted: 09/04/2008] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To estimate the frequency of the cystathionine beta-synthase deficiency caused by c.1105C>T mutation in Central Europe compared to Norway, and to examine the pathogenicity of the corresponding p.R369C mutant enzyme. STUDY DESIGN Mutation c.1105C>T was analyzed in 600 anonymous Czech newborn blood spots. Catalytic activity and quaternary structure of the p.R369C mutant was evaluated after expression in 2 cellular systems. RESULTS Population frequency of the c.1105C>T mutation was 0.005, predicting the birth prevalence of homocystinuria of 1:40000, which increased to 1:15500 in a model including 10 additional mutations. In Escherichia coli the p.R369C mutant misfolded, and its activity was severely reduced, and expression in Chinese hamster ovary cells enabled proper folding with activity decreased to 63% of the wild-type enzyme. This decreased activity was not due to impaired K(m) for both substrates but resulted from V(max) lowered to 55% of the normal cystathionine beta-synthase enzyme. CONCLUSIONS The c.1105C>T (p.R369C) allele is common also in the Czech population. Although the p.R369C mutation impairs folding and decreases velocity of the enzymatic reaction, our data are congruent with rather mild clinical phenotype in homozygotes or compound heterozygotes carrying this mutation.
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Affiliation(s)
| | | | | | | | | | - Viktor Kožich
- Institute of Inherited Metabolic Disorders, Charles University in Prague—1st Faculty of Medicine, Prague, Czech Republic
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Vyletal P, Sokolová J, Cooper DN, Kraus JP, Krawczak M, Pepe G, Rickards O, Koch HG, Linnebank M, Kluijtmans LAJ, Blom HJ, Boers GHJ, Gaustadnes M, Skovby F, Wilcken B, Wilcken DEL, Andria G, Sebastio G, Naughten ER, Yap S, Ohura T, Pronicka E, Laszlo A, Kožich V. Diversity of cystathionine beta-synthase haplotypes bearing the most common homocystinuria mutation c.833T>C: a possible role for gene conversion. Hum Mutat 2007; 28:255-64. [PMID: 17072863 PMCID: PMC2630376 DOI: 10.1002/humu.20430] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Homozygosity or compound heterozygosity for the c.833T>C transition (p.I278T) in the cystathionine beta-synthase (CBS) gene represents the most common cause of pyridoxine-responsive homocystinuria in Western Eurasians. However, the frequency of the pathogenic c.833C allele, as observed in healthy newborns from several European countries (qc.833C ≊ 3.3 × 10–3), is ∼20-fold higher than expected on the basis of the observed number of symptomatic homocystinuria patients carrying this mutation (qc.833C ≊ 0.18 × 10–3), implying clinical underascertainment. Intriguingly, the c.833C mutation is also present in combination with a 68-bp insertion, c.[833C; 844_845ins68], in a substantial proportion of chromosomes from nonhomocystinuric individuals worldwide. We have sought to study the relationship between the pathogenic and nonpathogenic c.833C-bearing chromosomes and to determine whether the pathogenic c.[833C; −] chromosomes are identical-by-descent or instead arose by recurrent mutation. Initial haplotype analysis of 780 randomly selected Czech and sub-Saharan African wild-type chromosomes, employing 12 intragenic markers, revealed 29 distinct CBS haplotypes, of which 10 carried the c.[833C; 844_845ins68] combination; none carried an isolated c.833C or c.844_845ins68 mutation. Subsequent examination of 69 pathogenic c.[833C; −] chromosomes, derived from homocystinuria patients of predominantly European origin, disclosed three unrelated haplotypes that differed from their wild-type counterparts by virtue of the presence of c.833C, thereby indicating that c.833T>C transition has occurred repeatedly and independently in the past. Since c.833T does not reside within an obvious mutational hotspot, we surmise that the three pathogenic and comparatively prevalent c.[833C; −] chromosomes may have originated by recurrent gene conversion employing the common nonpathogenic c.[833C; 844_845ins68] chromosomes as templates. Hum Mutat 28(3), 255–264, 2007. Published 2006 Wiley-Liss, Inc.†
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Affiliation(s)
- Petr Vyletal
- Center for Applied Genomics, Institute of Inherited Metabolic Disorders, Charles University 1st Faculty of MedicinePrague, Czech Republic
| | - Jitka Sokolová
- Center for Applied Genomics, Institute of Inherited Metabolic Disorders, Charles University 1st Faculty of MedicinePrague, Czech Republic
| | - David N. Cooper
- Institute of Medical Genetics, Cardiff UniversityCardiff, United Kingdom
| | - Jan P. Kraus
- Department of Pediatrics, University of Colorado School of MedicineAurora, Colorado
| | - Michael Krawczak
- Institut für Medizinische Informatik und Statistik, Christian-Albrechts UniversitätKiel, Germany
| | - Guglielmina Pepe
- Department of Medical and Surgical Critical Care, Center of Research, Transfer, High Education “DENOthe,” University of FlorenceFlorence, Italy
| | - Olga Rickards
- Centre of Molecular Anthropology for Ancient DNA Studies, Department of Biology, University of Rome “Tor Vergata,”Rome, Italy
| | - Hans G. Koch
- Department of Pediatrics, University Hospital MünsterMünster, Germany
| | - Michael Linnebank
- Department of Pediatrics, University Hospital MünsterMünster, Germany
- Department of Neurology, University Hospital BonnBonn, Germany
| | - Leo A. J. Kluijtmans
- Laboratory of Pediatrics and Neurology, University Medical Centre NijmegenThe Netherlands
| | - Henk J. Blom
- Laboratory of Pediatrics and Neurology, University Medical Centre NijmegenThe Netherlands
| | - Godfried H. J. Boers
- Department of Internal Medicine, University Hospital NijmegenNijmegen, The Netherlands
| | - Mette Gaustadnes
- Department of Clinical Biochemistry, Aarhus University HospitalAarhus, Denmark
| | - Flemming Skovby
- Department of Clinical Genetics, RigshospitaletCopenhagen, Denmark
| | - Bridget Wilcken
- The Children's Hospital at WestmeadSydney, New South Wales, Australia
| | - David E. L. Wilcken
- Cardiovascular Genetics Laboratory, Prince of Wales HospitalRandwick, New South Wales, Australia
| | - Generoso Andria
- Department of Paediatrics, Federico II UniversityNaples, Italy
| | | | - Eileen R. Naughten
- The National Centre of Inherited Metabolic Diseases, The Children's University HospitalDublin, Ireland
| | - Sufin Yap
- The National Centre of Inherited Metabolic Diseases, The Children's University HospitalDublin, Ireland
| | - Toshihiro Ohura
- Department of Pediatrics, Tohoku University School of MedicineSendai, Japan
| | - Ewa Pronicka
- Division of Metabolic Diseases, Department of Paediatrics, Children's Memorial Health InstituteWarsaw, Poland
| | - Aranka Laszlo
- Department of Pediatrics, Albert Szent-Gyorgyi Medical Center, University of SzegedSzeged, Hungary
| | - Viktor Kožich
- Center for Applied Genomics, Institute of Inherited Metabolic Disorders, Charles University 1st Faculty of MedicinePrague, Czech Republic
- *Correspondence to: Dr. Viktor Kožich, Institute of Inherited Metabolic Diseases, Charles University 1st Faculty of Medicine, Ke Karlovu 2, 128 08 Praha 2, Czech Republic. E-mail:
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