A GENE ENCODING ARGINYL-TRANSFER-RNA SYNTHETASE IS LOCATED IN THE UPSTREAM REGION OF THE LYSA GENE IN BREVIBACTERIUM-LACTOFERMENTUM - REGULATION OF ARGS-LYSA CLUSTER EXPRESSION BY ARGININE

The Brevibacterium lactofermentum argS gene, which encodes an arginyl-tRNA synthetase, was identified in the upstream region of the lysA gene. The cloned gene was sequenced; it encodes a 550-amino-acid protein with an Mr of 59,797. The deduced amino acid sequence showed 28% identical and 49% similar residues when compared with the sequence of the Escherichia coli arginyl-tRNA synthetase. The B. lactofermentum enzyme showed the highly conserved motifs of class I aminoacyl-tRNA synthetases. Expression of the argS gene in B. lactofermentum and E. coli resulted in an increase in aminoacyl-tRNA synthetase activity, correlated with the presence in sodium dodecyl sulfate-polyacrylamide gels of a clear protein band that corresponds to this enzyme. One single transcript of about 3,000 nucleotides and corresponding to the B. lactofermentum argS-lysA operon was identified. The transcription of these genes is repressed by lysine and induced by arginine, showing an interesting pattern of biosynthetic interlock between the pathways of both amino acids in corynebacteria.