The role of eIF-4C in protein synthesis initiation complex formation

Abstract

eIF-4C has a pronounced stimulatory effect on initiation complex formation with native 80-S ribosomes (80-Sn) as the only source of ribosomal subunits, but only a small effect when washed 40-S subunits are used.

eIF-4C is accessary to eIF-3 in dissociating 80-Sn ribosomes.

eIF-4C is present on 40-Sn but absent on 40-Sn dimers, which occur in preparations of native ribosomes and are as such inactive in protein synthesis.

eIF-4C dissociates 40-Sn dimers into active monomers. These results can be explained by assuming that the presence of eIF-4C on 40-Sn prevents:

1. (a) premature association with 60-S ribosomal subunits and

2. (b) dimerisation, thus increasing the rate and extent of initiation complex formation.