PKU mutation p.G46S prevents the stereospecific binding of l-phenylalanine to the dimer of human phenylalanine hydroxylase regulatory domain

João Leandro; Jaakko Saraste; Paula Leandro; Torgeir Flatmark

doi:10.1002/2211-5463.12175

PKU mutation p.G46S prevents the stereospecific binding of l-phenylalanine to the dimer of human phenylalanine hydroxylase regulatory domain

FEBS Open Bio. 2017 Jan 21;7(2):195-203. doi: 10.1002/2211-5463.12175. eCollection 2017 Feb.

Authors

João Leandro¹, Jaakko Saraste², Paula Leandro³, Torgeir Flatmark²

Affiliations

¹ 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.
² Department of Biomedicine University of Bergen Norway.
³ Metabolism and Genetics Group Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL) Faculty of Pharmacy University of Lisbon Portugal.

Abstract

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-RD ^1-118/19-118) [Patel D et al. (2016) Sci Rep doi: 10.1038/srep23748]. In this study, a fusion protein of the domain (MBP-(pep_Xa)-hPAH-RD ^1-120) 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.

Keywords: phenylalanine hydroxylase; regulatory domain; βαββαβ folds.