The nucleotide sequence of gltD gene encoding the small subunit of Rhodobacter sphaeroides glutamate synthase

We have determined the complete nucleotide sequence of a 2 387 bp chromosomal SalI-EcoRI fragment, which contains the structural gene(gltD) for the small subunit of Rhodobacter sphaeroides glutamate synthase, as well as the 5'- and 3'-flanking regions. An open reading frame of 1 242 base pairs was identified as the R. sphaeroides gltD gene. The MW of the small subunit, as deduced from the nucleotide sequence, was estimated to be 44 kD. A comparison of the nucleotide sequences revealed a high similarity among gltD genes of R. sphaeroides, Azospirillum brasilense and Escherichia coli. The deduced amino acid sequence of R. sphaeroides GltD showed a high similarity with that of A. brasilense GltD. The analysis of the binding domains of R. sphaeroides GltD was also carried out. The gltD-lacZ gene fusion was constructed and the expression of gltD-lacZ was analyzed under various growth conditions. The repressional expression of gltD-lacZ fusion was observed in the presence of 15 mM leucine.