This paper shows that the
phenylalanine-specific tRNA of Escherichia coli as well as the yellow lupin
methionine initiator
tRNAMet can be charged 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; 1 atm = 1.01 x 10(5) Pa). The esterification reaction takes places at the 3' end of the
tRNA molecules. The yield of Phe-
tRNAPhe or Met-
tRNAMet at high pressure is approximately 10 times lower than that of the enzymatic aminoacylation reaction. This reaction seems to be specific, and mis-aminoacylation of
tRNAPhe and
tRNAMet 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.