Substrate Specificity of Ribosomal Peptidyl Trausferase.

The effect of the nature of the amino acid residue on the acceptor activity of substrates of ribosomal peptidyl transferase was investigated. We tested 2'(3')-O-aminoacyladenosines conraining the following amino acid residues: L-alanine, L-glutamine, glycine, L-3-(1-benzyl-4-imidazolyl)-alanine, L-leucine, L-lysine, L-methionine, L-methionine S-oxide, L-phenylalanine, D-phenylalanine, L-proline, L-serine and L-valine as acceptors of the acylaminoacyl residue transferred from peptidyl-tRNA. The acceptor activity of these compounds was dependent on the nature of the side chain of the amino acid residues bound to adenosine. The acceptor activity was also affected by the nature of the donor tRNA derivative. With L-acetylphenylalanyl-tRNA or L-acetylleucine npetanucleotide fragments derived from L-acetylleucyl-tRNA donating the acetylphenylalanyl and the acetylleucyl residue, respectively, a high acceptor activity was shown by the basic 2'(3')-O-L-lysyladenosine or 2'(3')-O-L-3-(1-benzyL4-imidazolyl)-alanyladenosine which acted only as weak acceptors of lysine peptides from (Lys)_n-tRNA. The transfer reaction catalyzed by peptidyl transferase was stereospecific with respect to acceptor substrates. The acylaminoacyl residue was transferred from tRNA to 2'(3')-O-L-phenylalanyladenosine, whereas 2'(3')-O-D-phenylalanyladenosine, containing a D-phenylalanine residue, was completely inactive as acceptor. [ABSTRACT FROM AUTHOR]