Figure 1.

Binding of eIF1 to the 40S ribosomal subunit. (A) Interaction of 40S subunits with T7-Tag antibody agarose-immobilized eIF1 in an in vitro binding assay. Ribosomal protein S6 was visualized by Western blotting. (B) Presence of eIF1 in ribosomal complexes isolated from sucrose density gradients. Prior to centrifugation, 40S subunits were incubated with eIF1 and different combinations of eIF3, eIF2–ternary complex, and poly(U) RNA as indicated. eIF1 in fractions containing 40S subunits was detected by Western blotting using anti-T7 tag antibodies.