Nitric oxide (NO) is an important signaling molecule in eukaryotic and prokaryotic cells. A previous study revealed an NOS-independent NO production metabolic cycle in which the three nitrogen oxides, nitrate (NO3-), nitrite (NO2-) and NO were generated in the actinobacterium Streptomyces coelicolor A3(2). NO was suggested to act as a signaling molecule, functioning as a hormone that regulates secondary metabolism. Here, we demonstrate the NO-mediated regulation of the production of the blue pigmented antibiotic, actinorhodin (ACT), via the heme-based DevS/R two-component system (TCS). Intracellular NO controls the stabilization or inactivation of DevS, depending on the NO concentration. An electrophoretic mobility shift assay and chromatin immunoprecipitation-quantitative polymerase chain reaction analysis revealed the direct binding between DevR and the promoter region of actII-ORF4, resulting in gene expression. Our results indicate that NO simultaneously regulates the DevS/R TCS, thereby strictly controlling the secondary metabolism of S. coelicolor A3(2).
Importance
Diverse organisms, such as mammals, plants, and bacteria, utilize NO via well known signal transduction mechanisms. Many useful secondary metabolites producer Streptomyces genus bacteria had been also suggested the metabolisms regulated by endogenously produced NO; however, the regulatory mechanisms remain to be elucidated. In this study, we demonstrated the molecular mechanism by which endogenously produced NO regulates antibiotic production via DevS/R TCS in S. coelicolor A3 (2). NO serves as both a stabilizer and a repressor in the regulation of antibiotic production. This report shows the mechanism by which Streptomyces utilizes endogenously produced NO to modulate their normal life cycle. Moreover, this study implies that studying NO signaling in actinobacteria can help in the development of both clinical strategies against pathogenic actinomycetes and the actinobacterial industries.
Previous our studies revealed that a two-component system (TCS), DevS, and DevR, regulate both nitric oxide (NO) signaling and NO homeostasis in the actinobacterium Streptomyces coelicolor A3(2) M145, suggesting a reasonable system for NO-dependent metabolism. In this study, sequence alignment of DevR and DevR homologs found Asp66 (D66) and Thr196 (T196) as predicted phosphorylation sites of DevR. Phos-tag gel electrophoretic mobility shift assay suggested that D66 and T196 are involved in the phosphorylation of DevR. The respective point mutations of D66 and T196 significantly decreased the transcriptional activity of DevR, which affected nitrite production and aerial mycelium formation. These results suggested that both D66 and T196 of DevR are important for the regulation of NO homeostasis and signaling in S. coelicolor A3(2) M145.
Eukaryotic and prokaryotic cells utilize nitric oxide (NO) to regulate physiological functions. Besides its role as a producer of different bioactive substances,
Streptomyces
is suggested to be involved in mycelial development regulated by endogenously produced NO.
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