A wblA-binding protein, spiA, involved in streptomyces oxidative stress response

The Streptomyces coelicolor wblA gene is known to play a negative role in both antibiotic biosynthesis and the expression of genes responding to oxidative stress. Recently, WhcA, a WblA ortholog protein, was confirmed to interact with dioxygenase-encoding SpiA (stress protein interacting with WhcA) in Corynebacterium glutamicum. We describe here the identification of a SpiA ortholog SCO2553 protein (SpiA_sc) that interacts with WblA in S. coelicolor. Using heterologous expression in E. coli and in vitro pull-down assays, we show that WblA specifically binds SpiA_sc, and is influenced by oxidants such as diamide. These data indicate that the interaction between WblA and SpiA_sc is not only specific but also modulated by the redox status of the cell. Moreover, a spiA_sc-disruption mutant exhibited a less sensitive response to the oxidative stress induced by diamide present in solid plate culture. Real-time RT-PCR analysis also showed that transcription levels of oxidative stress response genes (sodF, sodF2, and trxB) were higher in the spiA_sc-deletion mutant than in wild-type S. coelicolor. These results show that SpiA_sc negatively regulates WblA during oxidative stress responses in S. coelicolor.