Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 264

RNA molecules are not simple linear chains but can form secondary structures that are important for RNA synthesis, translation, and assembly (Fig. 6.2). Structural features in RNA are identified by scanning the nucleotide sequence with software designed to fold the nucleic acid into energetically stable structures. Comparative sequence analysis can predict RNA secondary structures. For example, comparison of the RNA sequences of several related viruses might establish that the structure, but not the sequence, of a stem-loop is conserved. Direct evidence for specific RNA structures comes from experiments in which RNAs are treated with enzymes or chemicals that attack single- or double-stranded regions specifically. The results of such analyses can confirm that the predicted stem regions are base paired while loops are unpaired. Structures of RNA hairpins and pseudoknots have been determined by X-ray crystallography or nuclear magnetic resonance (Fig. 6.2C).