Crystal structures of CTP synthetase reveal ATP, UTP, and glutamine binding sites.
CTP synthetase (CTPs) catalyzes the last step in CTP biosynthesis, in which ammonia generated at the glutaminase domain reacts with the ATP-phosphorylated UTP at the synthetase domain to give CTP. Glutamine hydrolysis is active in the presence of ATP and UTP and is stimulated by the addition of GTP. We report the crystal structures of Thermus thermophilus HB8 CTPs alone, CTPs with 3SO4(2-), and CTPs with glutamine. The enzyme is folded into a homotetramer with a cross-shaped structure. Based on the binding mode of sulfate anions to the synthetase site, ATP and UTP are computer modeled into CTPs with a geometry favorable for the reaction. Glutamine bound to the glutaminase domain is situated next to the triad of Glu-His-Cys as a catalyst and a water molecule. Structural information provides an insight into the conformational changes associated with the binding of ATP and UTP and the formation of the GTP binding site.
Department of Chemistry, Graduate School of Science, Osaka University, Osaka 560-0043, Japan.
Masaru
M
Goto
Rie
R
Omi
Noriko
N
Nakagawa
Ikuko
I
Miyahara
Ken
K
Hirotsu
D001665:Binding Sites; D019731:Carbon-Nitrogen Ligases / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003570:Cytidine Triphosphate / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry; D005972:Glutaminase / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000737:chemistry*; D008958:Models, Molecular; D016963:Thermus thermophilus / Q000201:enzymology; D014544:Uridine Triphosphate / Q000737:chemistry*
D018698:Glutamic Acid; D003570:Cytidine Triphosphate; D006160:Guanosine Triphosphate; D005972:Glutaminase; D019731:Carbon-Nitrogen Ligases; C019951:CTP synthetase; D014544:Uridine Triphosphate