Figure 3.

Initiation of translation from the first and second AUG codons as a function of leader length. T7-derived transcripts from plasmids T3(8334), T6(8334), T9(8334), and T12(8334) were translated in the wheat germ system. T3(8334) was also transcribed with SP6 polymerase to obtain the indicated 32-nucleotide leader sequence. [³⁵S]methionine-labeled preCAT (•) and CAT (○) proteins were fractionated by polyacrylamide gel electrophoresis as in Figure 2; the resulting autoradiogram was quantified by densitometry. Protein yields in optical density units are plotted as a function of distance from the m7G cap to the preCAT start site (AUG #1).