title: The Monomeric Species of the Regulatory Domain of Tyrosine Hydroxylase Has a Low Conformational Stability.
abstract: Tyrosine hydroxylase (TyrH) catalyzes the hydroxylation of tyrosine to form 3,4-dihydroxyphenylalanine, the first step in the synthesis of catecholamine neurotransmitters. The protein contains a 159-residue regulatory domain (RD) at its N-terminus that forms dimers in solution; the N-terminal region of RDTyrH (residues 1-71) is absent in the solution structure of the domain. We have characterized the conformational stability of two species of RDTyrH (one containing the N-terminal region and another lacking the first 64 residues) to clarify how that N-terminal region modulates the conformational stability of RD. Under the conditions used in this study, the RD species lacking the first 64 residues is a monomer at pH 7.0, with a small conformational stability at 25 °C (4.7 ± 0.8 kcal mol(-1)). On the other hand, the entire RDTyrH is dimeric at physiological pH, with an estimated dissociation constant of 1.6 μM, as determined by zonal gel filtration chromatography; dimer dissociation was spectroscopically silent to circular dichroism but not to fluoresecence. Both RD species were disordered below physiological pH, but the acquisition of secondary native-like structure occurs at pHs lower than those measured for the attainment of tertiary native- and compactness-like arrangements.
authors.affiliation: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández , 03202 Elche (Alicante), Spain.|Biocomputation and Complex Systems Physics Institute , 50009 Zaragoza, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Neira
authors.affiliation: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández , 03202 Elche (Alicante), Spain.
authors.forename: Felipe
authors.initials: F
authors.lastname: Hornos
authors.affiliation: Department of Physical Chemistry, Biochemistry and Inorganic Chemistry, University of Almería , Agrifood Campus of International Excellence (ceiA3), Almería, Spain.
authors.forename: Julio
authors.initials: J
authors.lastname: Bacarizo
authors.affiliation: Department of Physical Chemistry, Biochemistry and Inorganic Chemistry, University of Almería , Agrifood Campus of International Excellence (ceiA3), Almería, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Cámara-Artigás
authors.affiliation: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández , 03202 Elche (Alicante), Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Gómez
mesh_terms: D002152:Calorimetry, Differential Scanning; D002850:Chromatography, Gel; D002942:Circular Dichroism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014446:Tyrosine 3-Monooxygenase / Q000737:chemistry*
chemical_list: D014446:Tyrosine 3-Monooxygenase