Isolation and analysis of three peroxide sensor regulatory gene homologs ahpC, ahpX and oxyR in Streptomyces viridosporus T7A - A lignocellulose degrading actinomycete

Increased lignolytic peroxidase activity has been demonstrated with the addition of sublethal doses of toxic H2O2 in Streptomyces viridosporus T7A. Until now, the effect of H2O2 at the molecular level has not been well characterized. Here, for the first time we report the isolation and analysis of three peroxide-induced gene homologs from S. viridosporus T7A; ahpC and ahpX(encoding alkyl hydroxyperoxidase subunits) and oxyR (encoding oxygen stress regulatory protein). The genome organization of these stress related genes were found to be divergently adjacent to each other. The protein sequence analysis of the oxyR homolog revealed a helix-turn-helix DNA-binding motif characteristic to the LysR of regulatory proteins induced by H2O2 The nucleotide sequence analysis of the intergenic region between ahpC and oxyR revealed that they shared a core T-n11-A, a signature protein-binding region of LysR family members. Based on similarities in sequence analysis, genetic organization, and the induction of lignin peroxidase activity upon exposure to hydrogen peroxide, we hypothesize a peroxide induction mechanism for the regulation of oxidative lignin biodegradation by S. viridosporus, possibly via use of OxyR which is also involved in regulating the peroxide stress response in this actinomycete.