Modified nucleoside-dependent transition metal binding to DNA analogs of the tRNA anticodon stem/loop domain
✍ Scribed by Anh T. Lam; Richard Guenther; Paul F. Agris
- Book ID
- 104639206
- Publisher
- Springer Netherlands
- Year
- 1995
- Tongue
- English
- Weight
- 729 KB
- Volume
- 8
- Category
- Article
- ISSN
- 1572-8773
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✦ Synopsis
Biologically active DNA analogs of tRNA Phe (tDNA phi) were used to investigate metal ion interaction with tRNA-like structures lacking the 2'OH. Binding of Mg 2 § to the 76 oligonucleotide tDNA ehe, monitored by circular dichroism spectroscopy, increased base stacking and thus the conformational stability of the molecule. Mg 2 § binding was dependent on a d(mSC) in the anticodon region. In contrast to Nlg 2 § Cd 2 § decreased base stacking interactions, thereby destabilizing the molecule. Since alterations in the anticodon region contributed to most of the spectral changes observed, detailed studies were conducted with anticodon hairpin heptadecamers (tDNAeAhe). The conformation of tDNA~h~-d(m5C) in the presence of 1 mM Cd 2+, Co 2+, Cr 2+, Cu 2+, Ni 2+, Pb 2+, VO 2+ or Zn 2 + differed significantly from that of the biologically active structure resulting from interaction with Mg 2 § Mn 2 + or Ca 2 +. Nanomolar concentrations of the transition metals were sufficient to denature the tDNAAe~-d(mSC) structure without catalyzing cleavage of the oligonucleotide. In the absence of Mg 2+ and at [Cd 2+] to [tDNAPAhe--d(mSC)] ratios of approximately 0.2-1.0, tDNAeAhe-d(mSC40) formed a stable conformation with one Cd 2 + bound with a K d = 3.7 x 10-7 M. In contrast to Mg 2 § Cd 2 + altered the DNA analogs without discriminating between modified and unmodified tDNAAe~. This ability of transition metals to disrupt higher order DNA structures, and possibly RNA, at /~M concentrations, in vitro, demonstrates that these structures are potential targets in chronic metal exposure, in vivo.