Spectrum and characterization of bi-allelic variants in MMAB causing cblB-type methylmalonic aciduria
| Autor: | Tanja Plessl, Céline Bürer, Caroline Frei, D. Sean Froese, Patrick Forny, Matthias R. Baumgartner |
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| Přispěvatelé: | University of Zurich, Froese, D Sean, Baumgartner, Matthias R |
| Rok vydání: | 2022 |
| Předmět: |
2716 Genetics (clinical)
610 Medicine & health Cobalamin Cofactor 03 medical and health sciences chemistry.chemical_compound Adenosine Triphosphate 0302 clinical medicine Mutase 1311 Genetics Genetics medicine Humans Missense mutation Proto-Oncogene Proteins c-cbl Allele Amino Acid Metabolism Inborn Errors Alleles Genetics (clinical) Adaptor Proteins Signal Transducing 030304 developmental biology 0303 health sciences Alkyl and Aryl Transferases biology Hydroxocobalamin Molecular biology Vitamin B 12 chemistry Methylmalonic aciduria 10036 Medical Clinic Mutation biology.protein CBLB Propionates 030217 neurology & neurosurgery medicine.drug |
| DOI: | 10.5167/uzh-213085 |
| Popis: | Pathogenic variants in MMAB cause cblB-type methylmalonic aciduria, an autosomal-recessive disorder of propionate metabolism. MMAB encodes ATP:cobalamin adenosyltransferase, using ATP and cob(I)alamin to create 5’-deoxyadenosylcobalamin (AdoCbl), the cofactor of methylmalonyl-CoA mutase (MMUT). We identified bi-allelic disease-causing variants in MMAB in 97 individuals with cblB-type methylmalonic aciduria, including 33 different and 16 novel variants. Missense changes accounted for the most frequent pathogenic alleles (p.(Arg186Trp), N = 57; p.(Arg191Trp), N = 19); while c.700C > T (p.(Arg234*)) was the most frequently identified truncating variant (N = 14). In fibroblasts from 76 affected individuals, the ratio of propionate incorporation in the presence and absence of hydroxocobalamin (PI ratio) was associated to clinical cobalamin responsiveness and later disease onset. We found p.(Arg234*) to be associated with cobalamin responsiveness in vitro, and clinically with later onset; p.(Arg186Trp) and p.(Arg191Trp) showed no clear cobalamin responsiveness and early onset. Mapping these and novel variants onto the MMAB structure revealed their potential to affect ATP and AdoCbl binding. Follow-up biochemical characterization of recombinant MMAB identified its three active sites to be equivalent for ATP binding, determined by fluorescence spectroscopy (Kd = 21 µM) and isothermal calorimetry (Kd = 14 µM), but function as two non-equivalent AdoCbl binding sites (Kd1 = 0.55 μM; Kd2 = 8.4 μM). Ejection of AdoCbl was activated by ATP (Ka = 24 µM), which was sensitized by the presence of MMUT (Ka = 13 µM). This study expands the landscape of pathogenic MMAB variants, provides association of in vitro and clinical responsiveness, and facilitates insight into MMAB function, enabling better disease understanding. |
| Databáze: | OpenAIRE |
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