Two-dimensional IR spectroscopy of the anti-HIV agent KP1212 reveals protonated and neutral tautomers that influence pH-dependent mutagenicity.
Antiviral drugs designed to accelerate viral mutation rates can drive a viral population to extinction in a process called lethal mutagenesis. One such molecule is 5,6-dihydro-5-aza-2'-deoxycytidine (KP1212), a selective mutagen that induces A-to-G and G-to-A mutations in the genome of replicating HIV. The mutagenic property of KP1212 was hypothesized to originate from its amino-imino tautomerism, which would explain its ability to base pair with either G or A. To test the multiple tautomer hypothesis, we used 2D IR spectroscopy, which offers subpicosecond time resolution and structural sensitivity to distinguish among rapidly interconverting tautomers. We identified several KP1212 tautomers and found that >60% of neutral KP1212 is present in the enol-imino form. The abundant proportion of this traditionally rare tautomer offers a compelling structure-based mechanism for pairing with adenine. Additionally, the pKa of KP1212 was measured to be 7.0, meaning a substantial population of KP1212 is protonated at physiological pH. Furthermore, the mutagenicity of KP1212 was found to increase dramatically at pH <7, suggesting a significant biological role for the protonated KP1212 molecules. Overall, our data reveal that the bimodal mutagenic properties of KP1212 result from its unique shape shifting ability that utilizes both tautomerization and protonation.
Departments of Chemistry and.
Chunte Sam
CS
Peng
Departments of Chemistry and Biological Engineering and Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; and.
Bogdan I
BI
Fedeles
Departments of Chemistry and Biological Engineering and Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; and.
Vipender
V
Singh
Departments of Chemistry and Biological Engineering and Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; and.
Deyu
D
Li
Biological Engineering and.
Tiffany
T
Amariuta
Departments of Chemistry and Biological Engineering and Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; and tokmakoff@uchicago.edu jessig@mit.edu.
John M
JM
Essigmann
Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, IL 60637 tokmakoff@uchicago.edu jessig@mit.edu.
Andrei
A
Tokmakoff
D019380:Anti-HIV Agents / Q000737:chemistry* / Q000633:toxicity*; D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000235:genetics; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000633:toxicity; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009152:Mutagenicity Tests; D009154:Mutation / Q000235:genetics; D011522:Protons; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism; D013696:Temperature; D014867:Water / Q000737:chemistry
C588297:5,6-dihydro-5-aza-2'-deoxycytidine; D019380:Anti-HIV Agents; D011522:Protons; D014867:Water; D003841:Deoxycytidine; D004247:DNA
KP1461; tautomerism; time-resolved spectroscopy; viral decay acceleration