ARGININE-BIOSYNTHESIS AND REGULATION IN LACTOBACILLUS-PLANTARUM - THECARA GENE AND THE ARGCJBDF CLUSTER ARE DIVERGENTLY TRANSCRIBED

A cluster of citrulline biosynthetic genes has been cloned and sequenc ed from a fragment of Lactobacillus plantarum CCM 1904 (ATCC 8014) DNA isolated as complementing a Bacillus subtilis argF mutation. The gene order was carA-argCJBDF, with carA transcribed divergently from the a rg cluster, Although other gram-positive bacteria show similar arg clu sters, this arrangement for carA is thus far unprecedented, Downstream from the arg cluster, two open reading frames (ORF7 and ORF8) having unknown functions were found. Sequence analysis of the end of a 10.5-k b cloned DNA fragment showed that argF was 3.5 kb from the IdhL gene c oding for L-(+)-lactate dehydrogenase. A tree representation of amino acid sequence clustering relationships of 31 ornithine carbamoyltransf erases (OTCases) from various organisms revealed two prokaryotic group s: one with ArgF of L. plantarum and one with ArgF of B. subtilis, whi ch are paralogous. This divergence was not observed in vivo because an L. plantarum argF mutant (AM 1215) harboring no OTCase activity was c omplemented by the argF genes of L. plantarum and B., subtilis. No OTC ase activity was detectable when L. plantarum was grown in the presenc e of saturating amounts of arginine or citrulline. Arginine may repres s the citrulline biosynthetic genes in L. plantarum by using 11 identi fied DNA motifs which resemble the Escherichia coli ARG box consensus and which are in most cases separated by multiples of 11 bp, correspon ding to a DNA helical turn, The carA and argCJBDF genes are divergentl y transcribed, Their putative promoters are 6 bp apart and are partial ly overlapped by putative ARG boxes, suggesting concerted transcriptio n regulation.