Structural basis for activation of the therapeutic L-nucleoside analogs 3TC and troxacitabine by human deoxycytidine kinase.Sabini, E., Hazra, S., Konrad, M., Burley, S.K., Lavie, A.
(2007) Nucleic Acids Res 35: 186-192
- PubMed: 17158155
- DOI: https://doi.org/10.1093/nar/gkl1038
- Primary Citation of Related Structures:
- PubMed Abstract:
L-nucleoside analogs represent an important class of small molecules for treating both viral infections and cancers. These pro-drugs achieve pharmacological activity only after enzyme-catalyzed conversion to their tri-phosphorylated forms. Herein, we report the crystal structures of human deoxycytidine kinase (dCK) in complex with the L-nucleosides (-)-beta-2',3'-dideoxy-3'-thiacytidine (3TC)--an approved anti-human immunodeficiency virus (HIV) agent--and troxacitabine (TRO)--an experimental anti-neoplastic agent. The first step in activating these agents is catalyzed by dCK. Our studies reveal how dCK, which normally catalyzes phosphorylation of the natural D-nucleosides, can efficiently phosphorylate substrates with non-physiologic chirality. The capability of dCK to phosphorylate both D- and L-nucleosides and nucleoside analogs derives from structural properties of both the enzyme and the substrates themselves. First, the nucleoside-binding site tolerates substrates with different chiral configurations by maintaining virtually all of the protein-ligand interactions responsible for productive substrate positioning. Second, the pseudo-symmetry of nucleosides and nucleoside analogs in combination with their conformational flexibility allows the L- and D-enantiomeric forms to adopt similar shapes when bound to the enzyme. This is the first analysis of the structural basis for activation of L-nucleoside analogs, providing further impetus for discovery and clinical development of new agents in this molecular class.
Department of Biochemistry and Molecular Genetics, University of Illinois Chicago, 900 S. Ashland (M/C 669), Chicago, IL 60607, USA.