Class distinctions

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Science  07 Nov 1997:
Vol. 278, Issue 5340, pp. 989
DOI: 10.1126/science.278.5340.989h

The enzymes that charge transfer RNAs (tRNAs) with their amino acids (tRNA synthetases, or RSs) have appeared to distribute into two classes in the same way in all organisms. In certain Archaea species (methanogens), however, no lysyl RSs, a class II RS, could be identified. Ibba et al. (p. 1119) have purified this enzyme from one organism and cloned the corresponding gene, which was found to correspond to unassigned open-reading frames in two other methanogens. The sequence suggests that this lysyl RS actually belongs to class I, which also raises questions concerning RS evolution.

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