Spectroscopic characterization of Mn2+ and Cd2+ coordination to phosphorothioates in the conserved A9 metal site of the hammerhead ribozyme
Journal Article
·
· Journal of Inorganic Biochemistry
- Trinity University, San Antonio, TX (United States)
- National Institute of Allergy and Infectious Diseases, Bethesda, MD (United States)
- Michigan State University, East Lansing, MI (United States)
- Brady-Built, Inc., Auburn, MA (United States)
- University of Oregon, Eugene, OR (United States)
- University of Georgia, Athens, GA (United States)
- University of California-Davis, CA (United States)
Phosphorothioate modifications have widespread use in the field of nucleic acids. As substitution of sulfur for oxygen can alter metal coordination preferences, the phosphorothioate metal-rescue experiment is a powerful method for identifying metal coordination sites that influence specific properties in a large RNAs. The A9/G10.1 metal binding site of the hammerhead ribozyme (HHRz) has previously been shown to be functionally important through phosphorothioate rescue experiments. While an A9-SRp substitution is inhibitory in Mg2+, thiophilic Cd2+ rescues HHRz activity. Mn2+ is also often used in phosphorothioate metal-rescue studies but does not support activity for the A9-SRp HHRz. Here, we use EPR, electron spin-echo envelope modulation (ESEEM), and X-ray absorption spectroscopic methods to directly probe the structural consequences of Mn2+ and Cd2+ coordination to Rp and Sp phosphorothioate modifications at the A9/G10.1 site in the truncated hammerhead ribozyme (tHHRz). The results demonstrate that while Cd2+ does indeed bind to S in the thio-substituted ligand, Mn2+ coordinates to the non–sulfur oxo group of this phosphorothioate, regardless of isomer. Computational models demonstrate the energetic preference of Mn—O over Mn—S coordination in metal-dimethylthiophosphate models. In the case of the tHHRz, the resulting Mn2+ coordination preference of oxygen in either Rp or Sp A9 phosphorothioates differentially tunes catalytic activity, with Mn—O coordination in the A9-SRp phosphorothioate enzyme being inhibitory.
- Research Organization:
- SLAC National Accelerator Laboratory, Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE
- Grant/Contract Number:
- AC02-76SF00515
- OSTI ID:
- 1981670
- Journal Information:
- Journal of Inorganic Biochemistry, Journal Name: Journal of Inorganic Biochemistry Journal Issue: C Vol. 230; ISSN 0162-0134
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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