STRUCTURAL ARRANGEMENT OF THE CODON ANTICODON INTERACTION AREA IN HUMAN PLACENTA RIBOSOMES - AFFINITY LABELING OF THE 40S SUBUNITS BY DERIVATIVES OF OLIGORIBONUCLEOTIDES CONTAINING THE AUG CODON

Using the derivatives of the oligoribonucleotides pAUGU(n) and AUGU(n) C (n = 0; 3) bearing an alkylating group at either the 5' or 3' end, r espectively (mRNA analogues), the affinity labelling of the human plac enta 40S ribosomal subunits has been investigated in model initiation complexes obtained in the presence of the ternary complex eIF-2.GTP.Me t-tRNA(Met)f. The regions of 18S rRNA and ribosomal proteins labelled with these mRNA analogues were identified. The sites of covalent attac hment of the pAUGU(n) derivatives with a reactive group at the 5' end were located between 18S rRNA positions 976 and 1164. The derivative o f AUGU3C with an alkylating group at the 3' end modified 18S rRNA main ly at the 593-673 region. The main targets of the 3' end derivative of AUGC were located between positions 1610 and 1869. The proteins S3/S3 a, S6, S7 and S14/S15 were modified by both types of the oligoribonucl eotide derivatives regardless of the point of the reactive group attac hment to the oligonucleotide moiety. The proteins S2 and S4 were modif ied by both the 3' end derivative of AUGC and 5' end derivative of pAU GU3; and the protein S8 was modified by the 3' end derivative of AUGC. The proteins S5 and S9 were labelled by the 5' end derivative of pAUG U3, and the protein S17 was modified by the 5' end derivative of pAUG.