Emerging structural themes in large RNA molecules

► Analysis of recent structures of large RNA molecules shows that they have organized domain architectures. ► The structures are stabilized by a wide range of tertiary interaction motifs. ► In many instances, homologous RNAs have a common structural core that is stabilized by different peripheral elements. ► Active sites and/or substrate binding sites are preassembled. ► Recognition involves both shape complementarity and specific molecular contacts.