GNRA tetraloop/helix interactions and GNRA tetraloop-like/helix interactions.

1“Indiv” indicates an individual structure that does not form an additional level of subgrouping based on superposition. “NTL” denotes a loop that does not consist of four nucleotides (non-tetraloop).2“++” indicates at most minor deviations between the electron density map and the specific modeled substructure (∼8–15 nts). “+” indicates a greater degree of unmodeled positive or negative electron density.3The E. coli ribosome substructures are nearly identical to Haloarcula, and are omitted from the table.