title: Crystal Structure of human pyridoxal kinase: structural basis of M(+) and M(2+) activation.
abstract: Pyridoxal kinase catalyzes the transfer of a phosphate group from ATP to the 5' alcohol of pyridoxine, pyridoxamine, and pyridoxal. In this work, kinetic studies were conducted to examine monovalent cation dependence of human pyridoxal kinase kinetic parameters. The results show that hPLK affinity for ATP and PL is increased manyfold in the presence of K(+) when compared to Na(+); however, the maximal activity of the Na(+) form of the enzyme is more than double the activity in the presence of K(+). Other monovalent cations, Li(+), Cs(+), and Rb(+) do not show significant activity. We have determined the crystal structure of hPLK in the unliganded form, and in complex with MgATP to 2.0 and 2.2 A resolution, respectively. Overall, the two structures show similar open conformation, and likely represent the catalytically idle state. The crystal structure of the MgATP complex also reveals Mg(2+) and Na(+) acting in tandem to anchor the ATP at the active site. Interestingly, the active site of hPLK acts as a sink to bind several molecules of MPD. The features of monovalent and divalent metal cation binding, active site structure, and vitamin B6 specificity are discussed in terms of the kinetic and structural studies, and are compared with those of the sheep and Escherichia coli enzymes.
authors.affiliation: Department of Medicinal Chemistry, School of Pharmacy and Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia 23219, USA.
authors.forename: Faik N
authors.initials: FN
authors.lastname: Musayev
authors.forename: Martino L
authors.initials: ML
authors.lastname: di Salvo
authors.forename: Tzu-Ping
authors.initials: TP
authors.lastname: Ko
authors.forename: Amit K
authors.initials: AK
authors.lastname: Gandhi
authors.forename: Ashwini
authors.initials: A
authors.lastname: Goswami
authors.forename: Verne
authors.initials: V
authors.lastname: Schirch
authors.forename: Martin K
authors.initials: MK
authors.lastname: Safo
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D002413:Cations, Divalent / Q000737:chemistry; D002414:Cations, Monovalent / Q000737:chemistry; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D029968:Escherichia coli Proteins / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D011188:Potassium / Q000737:chemistry*; D011731:Pyridoxal Kinase / Q000737:chemistry* / Q000378:metabolism; D012756:Sheep; D012964:Sodium / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D029968:Escherichia coli Proteins; D000255:Adenosine Triphosphate; D012964:Sodium; D011731:Pyridoxal Kinase; D008274:Magnesium; D011188:Potassium