Lee Soojin, Ahn Chiyoung, Park Eungsik, Hwang Deog Su, Yim Jeongbin
The National Creative Research Initiative Center for Genetic Reprogramming, Institute for Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea.
J Biochem Mol Biol. 2002 May 31;35(3):255-61. doi: 10.5483/bmbrep.2002.35.3.255.
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.
GTP环化水解酶I（E.C. 3.5.4.16）是一种同十聚体蛋白，它催化GTP转化为7,8 - 二氢新蝶呤三磷酸（H(2)NTP），这是蝶啶生物合成的第一步。有人提出该酶复合物可能由两个五聚体的二聚体组成，或者由紧密结合的二聚体的五聚体组成；然后酶的活性位点位于三个单体的界面处（Nar等人，1995a，b）。通过定点诱变制备的突变酶，我们表明GTP环化水解酶I的十聚体应由五个二聚体的五聚体组成，并且活性位点位于二聚体之间，这是通过一系列尺寸排阻色谱和重组实验分析得出的。我们还表明，残基Lys 136、Arg139和Glu152对于酶复合物从五个二聚体寡聚化为十聚体特别重要。
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