High-Resolution Crystal Structure of a Silver(I)-RNA Hybrid Duplex Containing Watson-Crick-like CSilver(I)C Metallo-Base Pairs

Metallo-base pairs have been extensively studied for applications in nucleic acid-based nanodevices and genetic code expansion. Metallo-base pairs composed of natural nucleobases are attractive because nanodevices containing natural metallo-base pairs can be easily prepared from commercially available sources. Previously, we have reported a crystal structure of a DNA duplex containing (THgT)-T-II base pairs. Herein, we have determined a high-resolution crystal structure of the second natural metallo-base pair between pyrimidine bases (CAgC)-C-I formed in an RNA duplex. One Ag-I occupies the center between two cytosines and forms a (CAgC)-C-I base pair through N3Ag(I)N3 linear coordination. The (CAgC)-C-I base pair formation does not disturb the standard A-form conformation of RNA. Since the (CAgC)-C-I base pair is structurally similar to the canonical Watson-Crick base pairs, it can be a useful building block for structure-based design and fabrication of nucleic acid-based nanodevices.