InterPro domain: IPR015963

Uridylate kinases (also known as UMP kinases) are key enzymes in the synthesis of nucleoside triphosphates. They catalyse the reversible transfer of the gamma-phosphoryl group from an ATP donor to UMP, yielding UDP, which is the starting point for the synthesis of all other pyrimidine nucleotides. The eukaryotic enzyme has a dual specificity, phosphorylating both UMP and CMP, while the bacterial enzyme is specific to UMP. The bacterial enzyme shows no sequence similarity to the eukaryotic enzyme or other nucleoside monophosphate kinases, but rather appears to be part of the amino acid kinase family. It is dependent on magnesium for activity and is activated by GTP and repressed by UTP [ 1 , 2 ]. In many bacterial genomes, the gene tends to be located immediately downstream of elongation factor T and upstream of ribosome recycling factor. A related protein family, believed to be equivalent in function is found in the archaea and in spirochetes.

Structurally, the bacterial and archaeal proteins are homohexamers centred around a hollow nucleus and organised as a trimer of dimers [ 3 , 4 ]. Each monomer within the protein forms the amino acid kinase fold and can be divided into an N-terminal region which binds UMP and mediates intersubunit interactions within the dimer, and a C-terminal region which binds ATP and contains a mobile loop covering the active site. Inhibition of enzyme activity by UTP appears to be due to competition for the binding site for UMP, not allosteric inhibition as was previously suspected.

This entry represents the bacterial/chloroplast uridine monophosphate kinase.

1. Escherichia coli UMP-kinase, a member of the aspartokinase family, is a hexamer regulated by guanine nucleotides and UTP. Biochemistry 34, 5066-74
2. Structural properties of UMP-kinase from Escherichia coli: modulation of protein solubility by pH and UTP. Biochemistry 35, 7003-11
3. The crystal structure of Pyrococcus furiosus UMP kinase provides insight into catalysis and regulation in microbial pyrimidine nucleotide biosynthesis. J. Mol. Biol. 352, 438-54
4. Structure of Escherichia coli UMP kinase differs from that of other nucleoside monophosphate kinases and sheds new light on enzyme regulation. J. Biol. Chem. 280, 25533-40