Sequence and molecular analysis of the Rhizobium etli glsA gene, encoding a thermolabile glutaminase

We sequenced a 2.1 kb fragment of DNA carrying the structural glsA gene, which codes for the Rhizobium etli thermolabile glutaminase (A). The glsA gene complements the R. etli LM16 mutant that lacks glutaminase A activity, and is expressed in the heterologous host Sinorhizobium meliloti. The deduced amino acid sequence consists of 309 residues, with a calculated molecular mass of 33 kDa. The amino acid sequence shares 53% and 43% identity with two hypothetical glutaminases of E. coli; 42% identity with liver-type; 38% identity with kidney-type glutaminase; 41% and 40% identity hypothetical glutaminases of Bacillus subtilis; and 41% and 37% identity with two putative glutaminases of Caenorhabditis elegans. The glsA gene represents the first glutaminase gene cloned and sequenced in prokaryotes.