PMID: 9321667

Authors:

Carter RJ, Baeyens KJ, SantaLucia J, Turner DH, Holbrook SR

Title:

The crystal structure of an RNA oligomer incorporating tandem adenosine-inosine mismatches.

Journal:

Nucleic Acids Res. 1997 Oct 15;25(20):4117-22.

Abstract:

The X-ray crystallographic structure of the RNA duplex [r(CGCAIGCG)]2 has been refined to 2.5 A. It shows a symmetric internal loop of two non-Watson-Crick base pairs which form in the middle of the duplex. The tandem A-I/I-A pairs are related by a crystallographic two-fold axis. Both A(anti)-I(anti) mismatches are in a head-to-head conformation forming hydrogen bonds using the Watson-Crick positions. The octamer duplexes stack above one another in the cell forming a pseudo-infinite helix throughout the crystal. A hydrated calcium ion bridges between the 3'-terminal of one molecule and the backbone of another. The tandem A-I mismatches are incorporated with only minor distortion to the backbone. This is in contrast to the large helical perturbations often produced by sheared G-A pairs in RNA oligonucleotides.