Biochemistry

Four of a Kind

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Science  22 Jun 2001:
Vol. 292, Issue 5525, pp. 2221
DOI: 10.1126/science.292.5525.2221b

The hypothesis that extant biological life, which relies largely on protein catalysts, arose from an RNA world requires that RNA catalysts existed that could synthesize proteins. This would require four reactions: (i) encoding of protein sequence, (ii) activation of amino acids, (iii) synthesis of aminoacyl-RNA, and (iv) formation of peptide bonds. It previously has been shown that RNA can mediate three of these reactions. The transfer of activated amino acids to an acceptor RNA can be catalyzed by small RNA molecules, and structural studies of the ribosome have revealed that peptide bond formation remains an RNA-catalyzed reaction. Also, there is evidence that some triplet codons are derived from ancient RNA binding sites for the cognate amino acids.

Kumar and Yarus have selected and characterized RNAs capable of activating amino acids. The triphosphate at the 5' end of the RNA reacts with amino acids, yielding pyrophosphate and the amino acid linked as a mixed anhydride to the RNA. This parallels the synthesis of aminoacyl adenylates catalyzed by modern-day aminoacyl-tRNA synthetases. — VV

Biochemistry40, 6998 (2001).

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