The universally conserved nucleotides of the small subunit ribosomal RNAs

G1338 and A1339 contact the P-site tRNA. The universally conserved G1338 and A1339 contact the minor groove of the anticodon stem of the P-site tRNA at base pairs 29–41 and 30–40. The flanking universal nucleotide G1337 forms a tertiary Watson–Crick base pair with C1237, and the nearly universal G944 forms a compact hydrogen-bonded network (Fig. 11), both of which help to fix the three-dimensional positions and orientations of G1338 and A1339.