1<p>“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).</p>2<p>“++” 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.</p>3<p>The <i>E. coli</i> ribosome substructures are nearly identical to <i>Haloarcula</i>, and are omitted from the table.</p
