C-Terminal Glycine-Gated Radical Initiation by GTP 3′,8-Cyclase in the Molybdenum Cofactor Biosynthesis
| Autor: | Bradley M. Hover, Kenichi Yokoyama |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: |
GTP'
Stereochemistry Hydrolases Protein Conformation Amino Acid Motifs Coenzymes Glycine Guanosine Cyclic pyranopterin monophosphate Guanosine triphosphate Biochemistry Cyclase Catalysis Cofactor Article chemistry.chemical_compound Colloid and Surface Chemistry Metalloproteins Metalloprotein Escherichia coli Carbon-Carbon Lyases chemistry.chemical_classification Binding Sites biology Chemistry Pteridines Nuclear Proteins General Chemistry Kinetics Mutation biology.protein Guanosine Triphosphate Molybdenum cofactor Molybdenum Cofactors Hydrogen |
| Popis: | The molybdenum cofactor (Moco) is an essential redox cofactor found in all kingdoms of life. Genetic mutations in the human Moco biosynthetic enzymes lead to a fatal metabolic disorder, Moco deficiency (MoCD). Greater than 50% of all human MoCD patients have mutations in MOCS1A, a radical S-adenosyl-l-methionine (SAM) enzyme involved in the conversion of guanosine 5'-triphosphate (GTP) into cyclic pyranopterin monophosphate. In MOCS1A, one of the frequently affected locations is the GG motif constituted of two consecutive Gly at the C-terminus. The GG motif is conserved among all MOCS1A homologues, but its role in catalysis or the mechanism by which its mutation causes MoCD was unknown. Here, we report the functional characterization of the GG motif using MoaA, a bacterial homologue of MOCS1A, as a model. Our study elucidated that the GG motif is essential for the activity of MoaA to produce 3',8-cH2GTP from GTP (GTP 3',8-cyclase), and that synthetic peptides corresponding to the C-terminal region of wt-MoaA rescue the GTP 3',8-cyclase activity of the GG-motif mutants. Further biochemical characterization suggested that the C-terminal tail containing the GG motif interacts with the SAM-binding pocket of MoaA, and is essential for the binding of SAM and subsequent radical initiation. In sum, these observations suggest that the C-terminal tail of MoaA provides an essential mechanism to trigger the free radical reaction, impairment of which results in the complete loss of catalytic function of the enzyme, and causes MoCD. |
| Databáze: | OpenAIRE |
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