engleski

In vivo recognition of eukaryal and bacterial tRNAsSer by heterologous seryl-tRNA synthetases

Aminoacyl-tRNA synthetases (aaRS) are important enzymes in protein biosynthesis that catalyze specific aminoacylation of cognate tRNAs. We have investigated the interaction of seryl-tRNA synthetases (SerRS) from different taxonomic domains with their cognate substrates in different in vivo systems. As representatives of eukaryal SerRSs, we chose two enzymes from Zea mays, and as representatives of archaeal enzymes two atypical SerRSs from methanogens Methanococcus jannaschii and Methanococcus maripaludis. In Zea mays, like in other plants, there are only two SerRSs: one is cytosolic (SerZMc) and the other seems to be organellar (SerZMm), dual-targeted to mitochondria and chloroplasts. Complementation of Saccharomyces cerevisiae strains, with disrupted alleles for cytosolic or organellar SerRS isoforms, showed that Zea mays SerZMc and SerZMm efficiently recognize yeast cytosolic or mitochondrial tRNAsSer, respectively. Besides, plant organellar enzyme can functionally replace bacterial SerRS, as previously shown by complementation of E. coli temperature sensitive serS mutant by the SerZMm gene (Rokov et all, 1998.). These results suggest close resemblance between bacterial and organellar SerRSs on one hand, and between two cytosolic SerRSs on the other hand. The methanogenic archaea contain atypical SerRSs that share very low sequence homology with counterparts from other organisms. Nevertheless, they seem to recognize well tRNASer from all three domains of life (Bilokapic et all, poster). In accordance with in vitro recognition, the gene for M. maripaludis SerRS, complemented the SES1 null allele yeast strain. However, no complementation of E. coli ts strain was observed. In vivo complementation experiments using heterologous SerRS genes, provide a useful tool for studying the evolution of tRNA:synthetase recognition. 1. Rokov J, Söll D, Weygand-Đurašević I.: Maize mitochondrial seryl-tRNA synthetase recognizes Escherichia coli tRNASer in vivo and in vitro. Plant Mol Biol. 1998 Oct ; 38(3):497-502. 2. Bilokapić S, Glavan F, Gruić-Sovulj I. and Weygand-Đurašević I: Differences in cross-domain tRNA recognition by the atypical seryl-tRNA synthetases from methanogenic archaea, POSTER

tRNASer ; seryl-tRNA synthetase ; Zea mays

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