Selective recognition of the native conformation of transfer ribonucleic acids by enzymes.

Abstract

Virtually absolute specificity for the native conformation of the sRNA substrate was observed in all 3 enzymatic processes investigated, 1 for completion of sRNA synthesis, and 2 for protein synthesis. While the requirement for the native conformation of sRNA in the reactions catalyzed by the aminoacyl-sRNA synthetases shows that the structural modification resulting in the denatured form prevents the enzymes from performing their catalytic functions, the ability of the penodate-oxidized sRNAleu to act as an inhibitor in its denatured conformation indicates that the enzyme recognition site on the sRNA must be sufficiently intact to permit some association between the denatured sRNA and its anunoacyl-sRNA synthetase. In view of the high degree of specificity of an ammoacyl-sRNA synthetase and its sRNA substrates, this finding cannot yet be generalized for the "denatured" forms of other sRNA''s. In the two reactions involving terminal addition of AMP on to sRNA and peptide bond formation, the relevant enzymes do not normally discriminate between different sRNA''s, but must recognize conformational features common to all sRNA''s. Therefore, the high degree of specificity displayed in these reactions in favor of the native conformation has 2 implications. One is that some structural feature(s) common to all native sRNA''s has been modified in the denatured form. The other is that there is great similarity in conformation of all sRNA''s.