title: Small aminothiol compounds improve the function of Arg to Cys variant proteins: effect on the human cystathionine β-synthase p.R336C.
abstract: The key regulatory point of L-methionine (Met) and L-homocysteine (Hcy) degradation is catalyzed by cystathionine beta-synthase (CBS). CBS deficiency is caused by mutations in CBS gene, often resulting in protein misfolding. The prevalence of CBS deficiency in Qatar is 1/1800, ∼200-fold higher than the worldwide prevalence of 1/344 000. Almost all patients bear the CBS p.R336C variant. More than 20 years ago, it was shown in vitro that two unrelated protein variants with a substitution of an arginine (Arg) residue by cysteine (Cys) could be rescued by cysteamine (mercaptoethylamine), likely via formation of a disulfide between Cys and cysteamine, functionally mimicking the wild-type (WT) Arg side-chain. Based on these findings, we aimed to study whether cysteamine was able to improve the function of p.R336C CBS variant. Additionally, we tested the effect of mercaptoethylguanidine (MEG), a compound with a guanidino and a thiol function that may resemble Arg structure better than cysteamine. Three purified recombinant CBS proteins (p.R336C, p.R336H and WT) were pre-incubated with cysteamine, MEG or Cys (as negative control), and CBS activity and stability were measured. Pre-incubation with cysteamine and MEG increased the enzymatic activity of the p.R336C protein, which was absent upon pre-incubation with Cys. The WT and the p.R336H variant enzyme activity presented no increase with any of the tested compounds. Our results show that cysteamine and MEG are able to specifically improve the function of the CBS p.R336C variant, suggesting that any Arg-to-Cys substitution accessible to these small molecules may be converted back to a moiety resembling Arg.
authors.affiliation: Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Metabolic Unit, Department of Clinical Chemistry, VU University Medical Centre, Amsterdam 1081 HV, The Netherlands and.
authors.forename: Marisa I S
authors.initials: MI
authors.lastname: Mendes
authors.affiliation: Metabolic Unit, Department of Clinical Chemistry, VU University Medical Centre, Amsterdam 1081 HV, The Netherlands and.
authors.forename: Desirée E C
authors.initials: DE
authors.lastname: Smith
authors.affiliation: Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon, Lisbon 1649-003, Portugal.
authors.forename: João B
authors.initials: JB
authors.lastname: Vicente
authors.affiliation: Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon, Lisbon 1649-003, Portugal.
authors.forename: Isabel
authors.initials: I
authors.lastname: Tavares De Almeida
authors.affiliation: Section of Clinical and Metabolic Genetics, Department of Pediatric, Hamad Medical Corporation, Doha, Qatar.
authors.forename: Tawfeg
authors.initials: T
authors.lastname: Ben-Omran
authors.affiliation: Metabolic Unit, Department of Clinical Chemistry, VU University Medical Centre, Amsterdam 1081 HV, The Netherlands and.
authors.forename: Gajja S
authors.initials: GS
authors.lastname: Salomons
authors.affiliation: Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon, Lisbon 1649-003, Portugal.
authors.forename: Isabel A
authors.initials: IA
authors.lastname: Rivera
authors.affiliation: Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Department of Biochemistry and Human Biology, Faculty of Pharmacy, University of Lisbon, Lisbon 1649-003, Portugal.
authors.forename: Paula
authors.initials: P
authors.lastname: Leandro
authors.affiliation: Metabolic Unit, Department of Clinical Chemistry, VU University Medical Centre, Amsterdam 1081 HV, The Netherlands and henk.blom@uniklinik-freiburg.de.
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Blom
mesh_terms: D001120:Arginine / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D003541:Cystathionine beta-Synthase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D005470:Fluorometry; D006801:Humans; D017433:Protein Structure, Secondary
chemical_list: D001120:Arginine; D003541:Cystathionine beta-Synthase; D003545:Cysteine