Cross-linking of Met-tRNAf to eIF-2/3 and to the ribosomal proteins S3a and S6 within the eukary- otic initiation complex, eIF-2-GMPPCP Met-tRNAf-small ribosomal subunit

In the quaternary initiation complex, eIF-2-GMPPCP-Met-tRNAf-40S ribosomal subunit, the Met-tRNAf can be cross-linked to the B subunit of initiation factor eIF-2 as well as to ribosomal proteins S3a and S6 by treatment with the bifunctional reagent, diepoxybutane. Using 40S subunits, modified in advance with the heterobifunctional reagent, methyl-p-azido-benzoylaminoacetimidate, Met-tRNAf is covalently bound to the same ribosomal proteins (S3a and S6) upon irradiation of the complex with ultraviolet light. Under both conditions proteins S3a and S6, together with a limited number of other ribosomal proteins, are covalently bound to 18S ribosomal RNA