Investigations on the messenger RNA binding site of eukaryotic ribosomes by using reactive oligo(U) derivatives

Dodecauridylate bearing a slowly alkylating reactive group in 5'-position, when bound as a mRNA analogue to rat liver ribosomes, labels preferentially proteins of the small ribosomal subunit, in particular, protein S 26.fDodecauridylate bearing an identical reactive group in 3'-position labels mainly rRNA o both subunits and proteins to less than 10%, among which S3/3a are the main targets. The results together with earlier findings support the localization of protein S 26 near the ribosomal P site and S 3/3a near the A site as well as the importance of rRNA of both subunits for interaction with mRNA when it passes the region in front of the decoding site.