Monitoring the enzyme expression in a respiratory chain of Corynebacterium glutamicum in a copper ion-supplemented culture medium
2015
Kusumoto, Tomoichirou | Aoyagi, Makoto | Sugiyama, Takahiko | Sakamoto, Junshi
Corynebacterium glutamicum has a branched respiratory chain: one of the branches is cytochrome bcc complex and cytochrome aa₃-type cytochrome c oxidase, and the other is cytochrome bd-type menaquinol oxidase. The factors that influence the expression patterns of these respiratory enzymes remain unclear. To investigate the expressional control mechanism of the enzymes, we have previously constructed a promoter assay system utilizing enhanced green fluorescence protein. Here, we monitored respiratory enzymes’ expression by using this system during growth in various culture media, with and without Cu²⁺ ion supplementation. The promoter activities of cytochrome aa₃ oxidase in the early stationary phase in the media supplemented with Cu²⁺ ion at 40 or 400 μM were significantly increased 1.49-fold or 1.99-fold, respectively, as compared to the control. Moreover, the H⁺/O ratio, or the proton-pumping activity of the cells, increased about 1.6 times by the Cu²⁺ supplementation. These facts indicate that copper ions can switch the branches.
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