On the Site of Esterification of Amino Acids to Soluble RNA^*

Abstract

Aminoacyladenosine was isolated from aminoacy 1-RN A by ribonuclease digestion and ion exclusion on DEAE-cellulose. To determine the position of esterification of the amino acid, 2,3-dihydropyran was used to block the unoccupied hydroxyl groups of the aminoacyl nucleoside, the amino acid was removed in mild alkali, and the hydroxyl group originally occupied by the amino acid was phosphory lated. Each step in the reaction sequence was carefully evaluated with model compounds. After removal of the protecting groups, 2' and 3' adenylic acids were isolated in a molar ratio of 1:2. A study of the comparative rates of acyl migration and hydrolysis in esters of glycerol, as models, shows that acyl equilibration between a and ß positions is rapid, exceeding the rate of hydrolysis by a factor of more than 6000 in the neutral and alkaline range. Tentative extrapolation to aminoacy 1-RN A suggests that aminoacyl 2' and 3' esters may be in base-catalyzed tautomeric equilibrium at pH values near neutrality.The binding of amino acids to soluble RNA (s-RNA) (Hoagland et al., 1957) has been shown to involve attachment to the 2' or 3' hydroxyl group of the adenosine residue which terminates the nucleic acid chain (Zachau et al., 1958;Preiss et al., 1959). Attachment by ester linkage was inferred from the ease of hydroxylaminolysis and alkaline hydrolysis of these compounds * This work was supported in part by a grant from the National Science Foundation.

Interaction of elongation factor Tu with 2'(3')-O-aminoacyloligonucleotides derived from the 3' terminus of aminoacyl-tRNA.

“…Needless to say, other compounds investigated such as C-A-Phe (la) are an equilibrium mixture of the 2' and 3' isomers. Because of the extremely fast 2' ; 3' acyl migration (22), compounds 1 may interact with the enzyme as either a 2' or 3' isomer, depending upon which one is required. Thus, under the assumptions that (a) the specificity of the interaction of AA-oligonucleotides possessing the sequence of the 3' terminus of AA-tRNA with EF-Tu mimics that of AA-tRNA and (b) the stereochemical arrangement of the 3'-terminal moiety of the molecule of models 2 and 3 is similar to that of natural riboderivatives 1, we are tempted to suggest that it is 2'-AA-tRNA which specifically interacts with EF-TuGTP.…”

Glycerophospholipid synthesis: improved general method and new analogs containing photoactivable groups.

“…29 and references cited therein). Migration, in general, is rapid and favors predominantly the 1-position.…”

Functional transfer RNAs with modifications in the 3'-CCA end: differential effects on aminoacylation and polypeptide synthesis.

“…Mutations were introduced into the cloned tRNAval gene by site-directed mutagenesis (17) (21). Samples (0.5 ml) were collected, and the A260 and radioactivity were determined.…”