Cloning and nucleotide sequence of the Butyrivibrio fibrisolvens gene encoding a type III glutamine synthetase.

A Butyrivibrio fibrisolvens glnA gene encoding glutamine synthetase (GS) was cloned on a recombinant plasmid pGS4 which enabled Escherichia coli glnA deletion mutants to utilize (NH4)2SO4 as a sole source of nitrogen. The nucleotide sequence of a 2423 bp DNA segment containing the GS-coding region of B. fibrisolvens was determined and the complete amino acid sequence (701 residues) was deduced. Comparisons of the derived B. fibrisolvens GS protein sequence with the amino acid sequences of GS from other bacteria indicate that it is the second reported example of a type III GS, originally identified in the obligate anaerobe Bacteroides fragilis. The presence of GS in B. fibrisolvens cells and the regulation of the cloned GS in E. coli cells was demonstrated by Western blot analysis.