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Table 1 Ribozyme activities relevant for the emergence of the translation machinery from the RNA world

From: On the origin of the translation system and the genetic code in the RNA world by means of natural selection, exaptation, and subfunctionalization

Reaction Characteristics of the ribozyme References
Aminoacyl adenylate synthesis Low efficiency formation of leucyl and phenylalanyl adenylates observed with a 114-nucleotide ribozyme. [132]
Self-aminoacylation Self-aminoacylation of a 43-nulceotide ribozyme with phenylalanine using phe-AMP as the substrate. A 77-nucleotide RNA catalyzed the same reaction with a specificity and aminoacylatin rate greater that those of PheRS. [51, 146]
RNA 3'-aminoacylation In-trans The smallest ribozyme capable of non-specific tRNA aminoacylation consists of 29 nucleotides. A 45-nucleotide ribozyme has been obtained with a broad spectrum of activity toward diverse tRNAs and amino acids. Larger ribozymes with highly specific and efficient aminoacylation activity reported. [51, 147, 148]
In vitro selected peptidyltransferase ribozymes Several ribozymes selected to form dipeptides from an amino acid esterified to AMP or a oligonucleotide and a free amino acid. Structural similarity observed between peptidyltransferase sibozymes and the relevant portion of 23S rRNA. Formation of Phe-Phe-tRNA reported for the 29-nucleotide aminoacylating ribozyme. [128, 129, 149, 150]
Ribosomal peptidyltransferase In the ribosomal large subunits, the peptidyltransferase center maps to an are containing only RNA, leading to the conclusion that the reaction is catalyzed by a ribozyme; however, identification of the active residues remains elusive. [151–154]
Ribonucleotide polymerization Ribozymes capable of extending a pre-annealed RNA primer by 10–14 nucleotides selected from a pool of RNA ligase ribozymes [53, 54]