Cysteinyl-tRNA formation: the last puzzle of aminoacyl-tRNA synthesis

With the exception of the methanogenic archaca Methanococess jannaschii and Methanobacterium theymoautotrophicum Delta H, all organisms surveyed conta in orthologs of Escherichia coli cysteinyl-tRNA synthetase (CysRS), The cha racterization of CysRS-encoding (cysS) genes and the demonstration of their ability to complement an E, coli cysS(up arrow S) mutant reveal that Metha nococcus maripaludis and. Methanosarcina barkeri, two other methanogenic ar chaea, possess canonical CysRS proteins, A molecular phylogeny inferred fro m 40 CysRS sequences indicates that the CysRS of M, maripaludis and Methano sarcina spp, are specific relatives of the CysRS of Pyrococcus spp, and Chl amydia, respectively, This result suggests that the CysRS gene was acquired by lateral gene transfer in at least one euryarchaeotic lineage, (C) 1999 Federation of European Biochemical Societies.