Structures of human deoxycytidine kinase product complexes

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Human deoxycytidine kinase (dCK) plays a crucial role in nucleotide biosynthesis and the phosphorylation of antiviral and anticancer prodrugs.
• Previous structural studies of dCK have reported its apo form and a dead-end complex with substrate and product (ADP or UDP).
• However, structures detailing dCK complexes with substrate or product molecules were lacking.

Purpose of the Study:

• To elucidate the structural basis of deoxycytidine kinase (dCK) activity by determining the structures of its product complexes.
• To compare the active site conformations of dCK in product complexes with previously reported structures.
• To provide structural insights into the phosphorylation mechanism of dCK for prodrug activation.

Main Methods:

• X-ray crystallography was employed to determine the three-dimensional structures of dCK.
• dCK complexes were crystallized with specific ligands: dCMP, UDP, and Mg2+ ion; and dAMP, UDP, and Mg2+ ion.
• Structural analysis and comparison of the obtained dCK-product complex structures were performed.

Main Results:

• The crystal structures of human deoxycytidine kinase (dCK) in complex with products dCMP, UDP, and Mg2+ ion were determined.
• Additionally, the structure of dCK in complex with dAMP, UDP, and Mg2+ ion was resolved.
• Structural comparisons revealed that the active site conformations of the reported product complexes are similar to those of a previously determined dead-end complex involving substrate and UDP.

Conclusions:

• The determined structures of dCK product complexes provide novel insights into the enzyme's catalytic mechanism.
• The observed similarity in active site conformations between product and dead-end complexes aids in understanding substrate binding and product release.
• These structural findings are significant for the rational design of novel prodrugs targeting dCK for therapeutic applications.