Modular structures in tRNAs and psaA RNAs. (A) Consensus diagram of tRNAs taken from the Rfam database  and drawn using the standard tRNA layout. A hairpin that is only sometimes present is shown (lower, right). In this case, the hairpin does not conserve obvious features, and is therefore shown in the "skeleton" style. Other consensus features of tRNAs are not depicted here. (B) Consensus diagram of psaA RNAs . The terminal loops of this RNA often adopt the UNCG tetraloop , but also often conform to the CUNG tetraloop  or an unstudied CYYGN pentaloop pattern. These distinct sequence features are drawn as modular structures, and were manually positioned near to their associated terminal loop. Other than this repositioning, the diagram is raw R2R output. Some additional annotation and sequence of the psaA motif is not shown here. A portion of this figure was adapted from a previous report .