Abstract
The rapid in vivo degradation of the potent human cytomegalovirus inhibitor 2-bromo-5,6-dichloro-1-(β-d-ribofuranosyl)benzimidazole (BDCRB) compared with a structural l-analog, maribavir (5,6-dichloro-2-(isopropylamino)-1-β-l-ribofuranosyl-1H-benzimidazole), has been attributed to selective glycosidic bond cleavage. An enzyme responsible for this selective BDCRB degradation, however, has not been identified. Here, we report the identification of two enzymes, 8-oxoguanine DNA glycosylase (OGG1) and N-methylpurine DNA glycosylase (MPG), that catalyze N-glycosidic bond cleavage of BDCRB and its 2-chloro homolog, 2,5,6-trichloro-1-(β-d-ribofuranosyl)benzimidazole, but not maribavir. To our knowledge, this is the first demonstration that free nucleosides are substrates of OGG1 and MPG. To understand how these enzymes might process BDCRB, docking and molecular dynamics simulations were performed with the native human OGG1 crystal coordinates. These studies showed that OGG1 was not able to bind a negative control, guanosine, yet BDCRB and maribavir were stabilized through interactions with various binding site residues, including Phe319, His270, Ser320, and Asn149. Only BDCRB, however, achieved orientations whereby its anomeric carbon, C1′, could undergo nucleophilic attack by the putative catalytic residue, Lys249. Thus, in silico observations were in perfect agreement with experimental observations. These findings implicate DNA glycosylases in drug metabolism.
Footnotes
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This work was made possible by National Institutes of Health Grants R01-GM37188 and P01-AI46390. P.L.L. was supported by National Institute of General Medical Sciences (NIGMS) Training Grant GM07767. The contents are solely the responsibility of the authors and do not necessarily represent the official views of NIGMS.
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.105.009209.
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ABBREVIATIONS: HCMV, human cytomegalovirus; BDCRB, 2-bromo-5,6-dichloro-1-(β-d-ribofuranosyl)benzimidazole; TCRB, 2,5,6-trichloro-1-(β-d-ribofuranosyl)benzimidazole; maribavir, 5,6-dichloro-2-(isopropylamino)-1-β-l-ribofuranosyl-1H-benzimidazole; FTCRI, 3-formyl-2,5,6-trichloro-1-(β-d-ribofuranosyl)indole; OGG1, 8-oxoguanine DNA glycosylase; MPG, N-methylpurine DNA glycosylase; PNP, purine nucleoside phosphorylase; TP, thymidine phosphorylase; TGT, tRNA-guanine transglycosylase; HPLC, high performance liquid chromatography; MD, molecular dynamics; h, human; m, murine; DMSO, dimethyl sulfoxide; GEO, Gene Expression Omnibus; DTT, dithiothreitol; RT, retention time; MOE, Molecular Operating Environment; PDB, Protein Data Bank; ds, double-stranded.
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The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material. -
↵1 Current affiliation: Genomics and Bioinformatics Group, Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland.
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↵2 Current affiliation: Institute for Biochemistry and Molecular Biology, University of Berne, Switzerland.
- Received December 31, 2005.
- Accepted March 20, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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