title: Biochemical characterization of oligomerization of Escherichia coli GTP cyclohydrolase I.
abstract: GTP cyclohydrolase I (E.C. 3.5.4.16) is a homodecameric protein that catalyzes the conversion of GTP to 7,8- dihydroneopterin triphosphate (H(2)NTP), the initial step in the biosynthesis of pteridines. It was proposed that the enzyme complex could be composed of a dimer of two pentamers, or a pentamer of tightly associated dimers; then the active site of the enzyme was located at the interface of three monomers (Nar et al. 1995a, b). Using mutant enzymes that were made by site-directed mutagenesis, we showed that a decamer of GTP cyclohydrolase I should be composed of a pentamer of five dimers, and that the active site is located between dimers, as analyzed by a series of size exclusion chromatography and the reconstitution experiment. We also show that the residues Lys 136, Arg139, and Glu152 are of particular importance for the oligomerization of the enzyme complex from five dimers to a decamer.
authors.affiliation: The National Creative Research Initiative Center for Genetic Reprogramming, Institute for Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea.
authors.forename: Soojin
authors.initials: S
authors.lastname: Lee
authors.forename: Chiyoung
authors.initials: C
authors.lastname: Ahn
authors.forename: Eungsik
authors.initials: E
authors.lastname: Park
authors.forename: Deog Su
authors.initials: DS
authors.lastname: Hwang
authors.forename: Jeongbin
authors.initials: J
authors.lastname: Yim
mesh_terms: D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D006136:GTP Cyclohydrolase / Q000737:chemistry* / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011621:Pteridines / Q000378:metabolism
chemical_list: D011621:Pteridines; D006160:Guanosine Triphosphate; D006136:GTP Cyclohydrolase