Cystathionine beta-synthase mutations: effect of mutation topology on folding and activity. 2010

Viktor Kozich, and Jitka Sokolová, and Veronika Klatovská, and Jakub Krijt, and Miroslav Janosík, and Karel Jelínek, and Jan P Kraus
First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Institute of Inherited Metabolic Disorders, Prague, Czech Republic. viktor.kozich@lf1.cuni.cz

Misfolding of mutant enzymes may play an important role in the pathogenesis of cystathionine beta-synthase (CBS) deficiency. We examined properties of a series of 27 mutant variants, which together represent 70% of known alleles observed in patients with homocystinuria due to CBS deficiency. The median amount of SDS-soluble mutant CBS polypeptides in the pellet after centrifugation of bacterial extracts was increased by 50% compared to the wild type. Moreover, mutants formed on average only 12% of tetramers and their median activity reached only 3% of the wild-type enzyme. In contrast to the wild-type CBS about half of mutants were not activated by S-adenosylmethionine. Expression at 18 degrees C substantially increased the activity of five mutants in parallel with increasing the amounts of tetramers. We further analyzed the role of solvent accessibility of mutants as a determinant of their folding and activity. Buried mutations formed on average less tetramers and exhibited 23 times lower activity than the solvent exposed mutations. In summary, our results show that topology of mutations predicts in part the behavior of mutant CBS, and that misfolding may be an important and frequent pathogenic mechanism in CBS deficiency.

UI MeSH Term Description Entries
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D002384 Catalysis The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction. Catalyses
D003080 Cold Temperature An absence of warmth or heat or a temperature notably below an accustomed norm. Cold,Cold Temperatures,Temperature, Cold,Temperatures, Cold
D003541 Cystathionine beta-Synthase A multifunctional pyridoxal phosphate enzyme. In the second stage of cysteine biosynthesis it catalyzes the reaction of homocysteine with serine to form cystathionine with the elimination of water. Deficiency of this enzyme leads to HYPERHOMOCYSTEINEMIA and HOMOCYSTINURIA. EC 4.2.1.22. Serine Sulfhydrase,beta-Thionase,Cystathionine Synthetase,Cystathionine beta Synthase,Sulfhydrase, Serine,Synthetase, Cystathionine,beta Thionase,beta-Synthase, Cystathionine
D004795 Enzyme Stability The extent to which an enzyme retains its structural conformation or its activity when subjected to storage, isolation, and purification or various other physical or chemical manipulations, including proteolytic enzymes and heat. Enzyme Stabilities,Stabilities, Enzyme,Stability, Enzyme
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D006712 Homocystinuria Autosomal recessive inborn error of methionine metabolism usually caused by a deficiency of CYSTATHIONINE BETA-SYNTHASE and associated with elevations of homocysteine in plasma and urine. Clinical features include a tall slender habitus, SCOLIOSIS, arachnodactyly, MUSCLE WEAKNESS, genu varus, thin blond hair, malar flush, lens dislocations, an increased incidence of MENTAL RETARDATION, and a tendency to develop fibrosis of arteries, frequently complicated by CEREBROVASCULAR ACCIDENTS and MYOCARDIAL INFARCTION. (From Adams et al., Principles of Neurology, 6th ed, p979) CBS Deficiency,Cystathionine beta-Synthase Deficiency Disease,Cystathionine Beta Synthase Deficiency,Deficiency Disease, Cystathionine beta-Synthase,CBS Deficiencies,Cystathionine beta Synthase Deficiency Disease,Deficiencies, CBS,Deficiency Disease, Cystathionine beta Synthase,Deficiency, CBS
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012995 Solubility The ability of a substance to be dissolved, i.e. to form a solution with another substance. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Solubilities

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