The universally conserved nucleotides of the small subunit ribosomal RNAs

Helices h18 and h34 combine to position A-site tRNA contacts. (A) In spite of its three single-base bulges and two 3-base bulge loops (Fig. 10), C1054 is the sole base that projects from helix h34, stabilized by numerous flanking tertiary interactions involving universally conserved nucleotides (Fig. 11). (B) Formation of the noncanonical A532–G1206 tertiary base pair (Fig. 10) positions G530 and C1054 to contact the anticodon loop of the A-site tRNA (magenta).