Structural basis for recognition of Co2+ by RNA aptamers

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• RNA aptamers are valuable tools for studying metal ion-RNA interactions.
• Understanding the structural basis of cobalt(II) ion recognition by RNA is essential for various applications.

Purpose of the Study:

• To elucidate the structural mechanisms by which RNA aptamers recognize and bind cobalt(II) ions.
• To identify key nucleotide residues and structural motifs involved in Co(2+) binding.

Main Methods:

• Nucleotide analog interference mapping (NAIM) using phosphorothioate analogs.
• Identification of target sites for DNA oligomer hybridization.
• RNase H digestion assays to assess RNA structure stability.

Main Results:

• Specific guanine residues (G27-G28 in aptamer 18, G25-G26 in aptamer 20) are critical for Co(2+) binding.
• Interference patterns highlight the involvement of tandem guanines in ion coordination via their N7 atoms.
• Common structural motifs, including loop E-like and kissing dimer, are implicated in Co(2+) recognition.
• Purine-rich regions with high interference values were identified as hybridization targets for DNA oligomers.
• DNA oligomer hybridization and subsequent RNase H digestion are sensitive to Co(2+) concentration, suggesting structural changes in aptamers.

Conclusions:

• Specific guanine bases are essential for forming the Co(2+) binding pocket in RNA aptamers.
• The N7 atom of tandem guanines likely participates in coordinating Co(2+) ions.
• RNA structural motifs and purine-rich regions play significant roles in metal ion binding and aptamer stability.