The structure of uridylate kinase with its substrates, showing the transition state geometry.
Uridylate kinase from Saccharomyces cerevisiae is a member of the nucleoside monophosphate (NMP) kinase family and catalyzes the reaction ATP+NMP<==>ADP+NDP with moderate specificity for UMP. The recombinant enzyme crystallized together with two substrate molecules. The structure was solved, by multiple isomorphous replacement and solvent flattening, at 3.0 A and then refined at 2.13 A resolution. The present R-factor is 19%. Superposition onto the structure of a substrate-free adenylate kinase revealed the motions induced by substrate binding. A further superposition onto an adenylate kinase with bound P1,P5-bis(5'-adenosyl)pentaphosphate (Ap5A), a two-substrate-mimicking inhibitor, failed to explain the UMP preference of the uridylate kinase, but superimposed the nucleosides and in particular the non-transferred phosphates at the ATP- and NMP-site rather well. The coincidence of the phosphates indicate strongly that these groups assume their final positions during catalysis. This locates the transition state, which can be modeled with reasonable geometry in agreement with an in-line associative SN2 mechanism.
Müller-Dieckmann
H J
HJ
Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Freiburg im Breisgau, Germany.
Schulz
G E
GE
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular / Q000379:methods; D004926:Escherichia coli; D005800:Genes, Fungal; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009703:Nucleoside-Phosphate Kinase / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013379:Substrate Specificity; D014542:Uridine Monophosphate / Q000378:metabolism*; D014961:X-Ray Diffraction
D011994:Recombinant Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D014542:Uridine Monophosphate; C023276:uridine monophosphate kinase; D009703:Nucleoside-Phosphate Kinase