Interaction of Transcriptional Repressor ArgR with Transcriptional Regulator FarR at theargBPromoter Region inCorynebacterium glutamicum
ABSTRACTInCorynebacterium glutamicum, the ArgR protein, a transcriptional repressor, affects the expression level of theargBgene through binding to its promoter region. TheargBpromoter region (positions −77 to −25) has been found byin vitroelectrophoretic mobility shift assay (EMSA) results andin silicoanalysis to be important for the DNA binding of ArgR. Proline supplementation prevented the DNA binding of ArgR to theargBpromoter region and triggered an increase of theargBmRNA level. Additional mutational analyses of theargBpromoter region found nucleotides critical for ArgR binding (G located at position −58, C at position −55, and A at position −41 of theargBpromoter) in that region. Another transcriptional repressor, FarR, was also demonstrated to bind to theargBpromoter region. This binding was delimited to positions −57 to −77 on theargBpromoter. FarR has only one putative binding domain located at positions −57 to −77, but this region exactly overlapped with the binding region located from positions −55 to −77 for the binding of ArgR within theargBpromoter; thus, if ArgR bound with theargBpromoter first, the binding of FarR was not observed in this region. However, if FarR bound to the binding domain located at positions −57 to −77 first, ArgR could bind other binding sites located at positions −49 to −25 within theargBpromoter. Finally, this study suggests that ArgR can affect FarR binding to theargBpromoter region, as protein binding is dominated by the protein most able to do so.