Fig. 3.

Hinge 1 lies within the neck (h28) of the 30S subunit. (A) Hinge 1 is positioned in the middle of helix h28, the covalent connection between the head and body domains. The cylinders represent helical axes flanking the articulation point in the classical (10) (0° of head rotation; teal) and chimeric (15) (21.3° of head rotation; magenta) structures. (B) Hinge 1 is located at a weak point in the G-C–rich helix h28 around the bulged G926, which is flanked by conserved G⋅U wobble pairs. (C) The major groove of h28, measured across P927 and P1383, widens by >3 Å as a function of increasing head rotation (CC = 0.83; the correlation is represented with a trendline).