AFFINITY MODIFICATION OF 40S-SUBUNITS FROM HUMAN PLACENTA BY PAUG ANDPAUGU(3) DERIVATIVES

The affinity modification of 40S subunits from human placenta by 4-(N- 2-chloroethyl-N-methylami-no)benzylmethyl [P-32]phosphamides of oligor ibonucleotides pAUG and pAUGU3 was investigated. Covalent binding of p AUG and pAUGU3 derivatives to subunits was observed within the complex es with 40S subunits obtained in the presence of Met-tRNA(f) . eIF-2 . GTP. Both the proteins and the rRNA were modified. The 18S rRNA fragm ents containing the covalent binding sites were identified: segment 10 58-1164 for the pAUG derivative and segment 976-1057 for the pAUG and pAUGU3 derivatives. Comparison of these data with results of the affin ity modification of 80S ribosomes from human placenta by tri- and hexa uridylate derivatives allowed us to conclude that the location of the trinucleotide template in the codon-anticodon interaction site is stro ngly affected by the presence of the neighboring codon in the A-site, regardless of the presence of a tRNA molecule at that site. The large subunit does not introduce significant alterations into the structural organization of the codon-anticodon interaction region.