Fig. 4.

Molecular models for expansion segments ES3^S/ES6^S, ES7^L, and ES27^L. (A) Isolated density for ES6^Sd (blue) and ES3^Sa,c (gold) on the 40S subunit (Left) and transparent with a molecular model (Center). rRNA secondary structure prediction highlighting interaction between the loop of ES6^Sd and the bulge in ES3^Sc (Right), as proposed by ref. 59. (B) Isolated density for ES7^L from T. aestivum (T. a., blue) and S. cerevisiae (S. c., gold) on the 80S ribosome (Left) and transparent with a molecular model (Center). Ribosomal proteins L28e (red) stabilizes ES7^La in the T. aestivum 80S ribosome, whereas the extension of r-protein L6e appears to pass through the three-way junction formed by helices ES7^Lc–e (Right). Molecular models for the (gold) and (blue) positions (Left), as observed in S. cerevisiae 80S ribosomes (Thumbnail Insets) (39) and an intermediate position (, gray) observed in the T. aestivum 80S ribosome. In yeast, r-protein L34e (green) and L38e (red) interact with the and positions, respectively. The tunnel exit (TE) and L1 stalk (L1) are indicated for reference. (C) Schematic (Top Right) and molecular model (Middle Right) indicating that the interchange between the (gold) and (blue) positions involves a rotation of ∼110° of ES27^La–c relative to H63. Secondary structure for the junctions of S. cerevisiae ES27^La–c and H63.