Co-transcription of Rhizobium meliloti lysyl-tRNA synthetase and glutamyl-tRNA synthetase genes

An open reading frame encoding a putative polypeptide very similar to sever al lysyl-tRNA synthetases was found 10 nucleotides downstream of Rhizobium meliloti gltX encoding glutamyl-tRNA synthetase. Expression of this gene co mplemented a mutation in lysS of Escherichia coli and led to the overexpres sion of a polypeptide of the expected mass (62 kDa), thus confirming that i t encodes R. meliloti lysyl-tRNA synthetase. Reverse transcription/polymera se chain reaction was used to demonstrate that this lysS gene is co-transcr ibed with gltX in R. meliloti. This is the first reported case of two immed iately adjacent and co-transcribed genes encoding aminoacyl-tRNA synthetase s. (C) 1999 Federation of European Biochemical Societies.