FIG. 3.
(A) Primer extension inhibition (toeprint) assays using leaderless aph mRNA. The two-position toeprint signal in lanes 5 and 6 indicating a ternary complex with aph mRNA (0.2 pmol), low-salt-washed S. lividans 70S ribosomes (2 or 4 pmol), and tRNAfMet (10 pmol) is marked with a double arrowhead. (B) Coelectrophoresis of toeprint reaction mixtures containing leaderless aph mRNA with a DNA sequencing ladder. Mixtures contained 0.2 pmol of aph mRNA, 4 pmol of 30S subunits, 4 pmol of IF1 and IF2, and 10 pmol of initiator tRNA, when present. The first five codons of aph coding sequence are indicated, with the start codon in bold. The aph mRNA used is 89 nucleotides long.