ROCR, A NOVEL REGULATORY PROTEIN CONTROLLING ARGININE UTILIZATION IN BACILLUS-SUBTILIS, BELONGS TO THE NTRC NIFA FAMILY OF TRANSCRIPTIONAL ACTIVATORS/

Bacillus subtilis can use ammonium and various amino acids as sole nit rogen sources. The utilization of arginine or ornithine is abolished i n a sigma L-deficient strain of B. subtilis, indicating that one or se veral genes involved in this pathway are transcribed by a sigma L-RNA polymerase holoenzyme. Three B. subtilis genes, called rocA, rocB, and rocC, which seem to form an operon, mere found near the sacTPA locus (P. Glaser, F. Kunst, M. Arnaud, M.-P. Coudart, W. Gonzales, M.-F. Hul lo, M. Ionescu, B. Lubochinsky, L. Marcelino, I. Moszer, E. Presecan, M. Santana, E. Schneider, J. Schweizer, A. Vertes, G. Rapoport, and A. Danchin, Mol. Microbiol. 10:371-384, 1993). The expression of this pu tative operon is induced by arginine and is sigma L dependent. Mutants impaired in the transcription of rocA were obtained. One of these mut ants was used as recipient to clone and sequence a new regulatory gene , called rocR. This gene encodes a polypeptide of 52 kDa which belongs to the NtrC/NifA family of transcriptional activators. Upstream activ ating sequences highly similar to those of NtrC in Escherichia coli we re also identified upstream from the rocABC genes. A B. subtilis strai n containing a rocR null mutation is unable to use arginine as the sol e nitrogen source, indicating that RocR is a positive regulator of arg inine catabolism. After LevR, RocR is the second example of an activat or stimulating sigma 54-dependent promoters in gram-positive bacteria.