Emerging structural themes in large RNA molecules

Extensive networks of tertiary interactions give rise to unique, highly organized domain architectures that characterize the three-dimensional structure of large RNA molecules. Formed by stacked layers of a near-planar arrangement of contiguous coaxial helices, large RNA molecules are relatively flat in overall shape. The functional core of these molecules is stabilized by a diverse set of tertiary interaction motifs that often bring together distant regions of conserved nucleotides. Although homologous RNAs from different organisms can be structurally diverse, they adopt a structurally conserved functional core that includes preassembled active and/or substrate binding sites. These findings broaden our understanding of RNA folding and tertiary structure stabilization, illustrating how large, complex RNAs assemble into unique structures to perform recognition and catalysis. ⺠Analysis of recent structures of large RNA molecules shows that they have organized domain architectures. ⺠The structures are stabilized by a wide range of tertiary interaction motifs. ⺠In many instances, homologous RNAs have a common structural core that is stabilized by different peripheral elements. ⺠Active sites and/or substrate binding sites are preassembled. ⺠Recognition involves both shape complementarity and specific molecular contacts.