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 gen e. 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% ident ical and 49% similar residues when compared with the sequence of the E scherichia coli arginyl-tRNA synthetase. The B. lactofermentum enzyme showed the highly conserved motifs of class I aminoacyl-tRNA synthetas es. Expression of the argS gene in B. lactofermentum and E. coli resul ted in an increase in aminoacyl-tRNA synthetase activity, correlated w ith the presence in sodium dodecyl sulfate-polyacrylamide gels of a cl ear protein band that corresponds to this enzyme. One single transcrip t of about 3,000 nucleotides and corresponding to the B. lactofermentu m argS-lysA operon was identified. The transcription of these genes is repressed by lysine and induced by arginine, showing an interesting p attern of biosynthetic interlock between the pathways of both amino ac ids in corynebacteria.