The non-enzymatic specific aminoacylation of transfer RNA at high pressure

Abstract

This paper shows that the phenylalanine-specific tRNA of Escherichia coli as well as the yellow lupin methionine initiator tRNA Met can be charge specifically with phenylalanine and methionine, respectively, in the absence of specific aminoacyl-tRNA synthetases, under high pressure of a maximum of 6 kbar (1 bar = 10 5 Pa; 1atm = 1.01 × 10 5 Pa). The esterification reaction takes places at the 3′ end of the tRNA molecules. The yield of Phe-tRNA Phe or Met-tRNA Met at high pressure is ∼10 times lower than that of the enzymatic aminoacylation reaction. This reaction seems to be specific, and mis-aminoacylation of tRNA Phe and tRNA Met with serine is negligible. It is well known that tRNA undergoes conformational changes during interaction with an aminoacyl-tRNA synthetase. Similarly, on the basis of circular dichroism spectra, we showed that the conformation of tRNA at high pressure differs slightly from its original A-RNA form. Therefore, it can be speculated that the chargeable conformation of tRNA induced by the aminoacyl-tRNA synthetase during enzymatic aminoacylation and the one created at high pressure are similar and are most probably formed by a dehydration mechanism. We think that the ‘unique’ tertiary structure of tRNA existing under high pressure creates an active centre which might itself catalyse ester bond formation. Therefore, the structure of the amino acid stem of tRNA may determine (code) the charging of the particular amino acid to specific tRNA. This code is clearly distinct from the rules of the classical genetic code.