CLONING OF THE GLUTAMINE-SYNTHETASE GENE FROM GROUP-B STREPTOCOCCI

The glnA gene from the human pathogen Streptococcus agalactiae was clo ned from a genomic library prepared with the lambda phage vector lambd a DASHII, A 4,6-kb DNA fragment of one of the recombinant phages was s ubcloned in pUC18, This Escherichia coli clone expressed a 52-kDa prot ein encoded by a 1,341-bp open reading frame, The nucleotide sequence of the open reading frame and the deduced amino acid sequence shared a significant degree of homology with the sequences of other glutamine synthetases (GS), The highest homology was between our deduced protein and GS of gram-positive bacteria such as Bacillus subtilis;, Bacillus cereus, and Staphylococcus aureus. Plasmids with the cloned streptoco ccal glnA were able to complement E, coli glnA mutants grown on minima l media, Rabbit antisera to streptococcal GS recombinant protein recog nized not only the recombinant protein but also a similar-sized band i n mutanolysin extracts of all group B streptococcal strains tested, re gardless of polysaccharide type or surface protein profile, The amino acid sequence of the deduced protein had similarities to other strepto coccal cell-surface-bound proteins, The possible functional role of th e immunological features of streptococcal GS is discussed.