The effect of ArgR-DNA binding affinity on ornithine production in Corynebacterium glutamicum.

pEMBTL-SY1, which can over produce the ArgR protein in Corynebacterium glutamicum, was constructed. The DNA-binding affinity of ArgR was analyzed using a Chromatin Immunoprecipitation (ChIP) assay. The level of ArgR protein expression in the plasmid-carrying C. glutamicum (pEMBTL-SY1) was higher than that in the wild-type strain. On the other hand, there was no increase in the DNA-binding affinity of ArgR on the upstream of argB and the level of ornithine production. The DNA-binding affinity of ArgR on the arg operon and the level of ornithine production in the presence of three metabolites, ornithine, arginine, and proline, were examined as feedback controlling effectors in the arginine biosynthesis pathway in C. glutamicum. The ChIP assay showed that the supplemented metabolites altered the ArgR-binding affinity on the upstream of argB, which is consistent with the change in ornithine production. This suggests that the regulation of ornithine biosynthesis by the transcriptional regulator, ArgR, depends on the DNA-binding affinity of the arg operon, which is regulated by the feedback controlling effectors, rather than on the level of ArgR protein expression.