Human aromatic amino acid decarboxylase is an asymmetric and flexible enzyme: Implication in aromatic amino acid decarboxylase deficiency.

Autor: Bisello G; Department of Neuroscience, Biomedicine and Movement Sciences, Section of Biological Chemistry, Verona, Italy., Ribeiro RP; Department of Biotechnology, University of Verona, Verona, Italy., Perduca M; Department of Biotechnology, University of Verona, Verona, Italy., Belviso BD; National Research Council (CNR), Institute of Crystallography, CNR, Bari, Italy., Polverino De' Laureto P; Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy., Giorgetti A; Department of Biotechnology, University of Verona, Verona, Italy., Caliandro R; National Research Council (CNR), Institute of Crystallography, CNR, Bari, Italy., Bertoldi M; Department of Neuroscience, Biomedicine and Movement Sciences, Section of Biological Chemistry, Verona, Italy.
Jazyk: angličtina
Zdroj: Protein science : a publication of the Protein Society [Protein Sci] 2023 Aug; Vol. 32 (8), pp. e4732.
DOI: 10.1002/pro.4732
Abstrakt: Human aromatic amino acid decarboxylase (AADC) is a pyridoxal 5'-phosphate-dependent enzyme responsible for the biosynthesis of dopamine and serotonin, essential neurotransmitters involved in motor and cognitive abilities. Mutations in its gene lead to AADC deficiency, a monogenic rare neurometabolic childhood parkinsonism characterized by severe motor and neurodevelopmental symptoms. Here, for the first time, we solved the crystal structure of human holoAADC in the internal aldimine (1.9 Å) and in the external aldimine (2.4 Å) of the substrate analog L-Dopa methylester. In this intermediate, the highly flexible AADC catalytic loop (CL) is captured in a closed state contacting all protein domains. In addition, each active site, composed by residues of both subunits, is connected to the other through weak interactions and a central cavity. By combining crystallographic analyses with all-atom and coarse-grained molecular dynamics simulations, SAXS investigations and limited proteolysis experiments, we realized that the functionally obligate homodimeric AADC enzyme in solution is an elongated, asymmetric molecule, where the fluctuations of the CL are coupled to flexibility at the edge between the N-terminal and C-terminal domains. The structural integrity of this peripheral protein region is essential to catalysis, as assessed by both artificial and 37 AADC deficiency pathogenic variants leading to the interpretation that structural dynamics in protein regions far from the active site is essential for CL flexibility and the acquirement of a correct catalytically competent structure. This could represent the molecular basis for pathogenicity prediction in AADC deficiency.
(© 2023 The Authors. Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.)
Databáze: MEDLINE
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