Cytochrome < b > < i > bcc-aa3 < /i > < /b > Oxidase Supercomplexes in the Aerobic Respiratory Chain of < b > < i > Streptomyces coelicolor < /i > < /b > A3(2)

Streptomyces coelicolor A3(2), an obligately aerobic, oxidase-positive, and filamentous soil bacterium, lacks a soluble cytochromec in its respiratory chain, having instead a membrane-associated dihemec-type cytochrome, QcrC. This necessitates complex formation to allow electron transfer between the cytochromebcc andaa3 oxidase respiratory complexes. Combining genetic complementation studies with in-gel cytochrome oxidase activity staining, we demonstrate that the completeqcrCAB-ctaCDFE gene locus on the chromosome, encoding, respectively, thebcc andaa3 complexes, is required to manifest a cytochrome oxidase enzyme activity in both spores and mycelium of aqcr-cta deletion mutant. Blue-native-PAGE identified a cytochromeaa3 oxidase complex of approximately 270 kDa, which catalyzed oxygen-dependent diaminobenzidine oxidation without the requirement for exogenously supplied cytochromec, indicating association with QcrC. Furthermore, higher molecular mass complexes were identified upon addition of soluble cytochromec, suggesting the supercomplex is unstable and readily dissociates into subcomplexes lacking QcrC. Immunological and mass spectrometric analyses of active, high-molecular mass oxidase-containing complexes separated by clear-native PAGE identified key subunits of both thebcc complex and theaa3 oxidase, supporting supercomplex formation. Our data also indicate that the cytochromeb QcrB of thebcc complex is less abundant in spores compared with mycelium.J Mol Microbiol Bi...
Source: Journal of Molecular Microbiology and Biotechnology - Category: Microbiology Source Type: research