PKU mutation p.G46S prevents the stereospecific binding of l-phenylalanine to the dimer of human phenylalanine hydroxylase regulatory domain.
Mammalian phenylalanine hydroxylase (PAH) has a potential allosteric regulatory binding site for l-phenylalanine (l-Phe), in addition to its catalytic site. This arrangement is supported by a crystal structure of a homodimeric truncated form of the regulatory domain of human PAH (hPAH-RD1-118/19-118) [Patel Det al. (2016)Sci Repdoi: 10.1038/srep23748]. In this study, a fusion protein of the domain (MBP-(pepXa)-hPAH-RD1-120) was overexpressed and recovered in a metastable and soluble state, which allowed the isolation of a dimeric and a monomeric fusion protein. When cleaved from MBP, hPAH-RD forms aggregates which are stereospecifically inhibited by l-Phe (> 95%) at low physiological concentrations. Aggregation of the cleaved dimer of the mutant form hPAH-G46S-RD was not inhibited by l-Phe, which is compatible with structurally/conformationally changed βαββαβ ACT domain folds in the mutant.
Department of Biomedicine University of Bergen Norway; Metabolism and Genetics Group Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL) Faculty of Pharmacy University of Lisbon Portugal.
João
J
Leandro
Department of Biomedicine University of Bergen Norway.
Jaakko
J
Saraste
Metabolism and Genetics Group Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL) Faculty of Pharmacy University of Lisbon Portugal.
Paula
P
Leandro
Department of Biomedicine University of Bergen Norway.
Torgeir
T
Flatmark
phenylalanine hydroxylase; regulatory domain; βαββαβ folds