Photoregulation of Respiratory Activity in the Cyanophyte Synechocystis PCC 6714: the Possibility of the Simultaneous Regulation of the Amount of PS I Complex and the Activity of Respiratory Terminal Oxidase in Thylakoids

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Respiration of the cyanophyte Synechocystis PCC 6714 was studied in relation to conditions for cell growth. Under our experimental conditions, the KCN-sensitive O_2-uptake observed with intact cells was found to be limited at the step catalyzed by the terminal oxidase in thylakoids, indicating that the activity of O_2-uptake by intact cells corresponds to that of the terminal oxidase in thylakoids. The activity was found to be variable depending on the growth conditions; it was higher under conditions where the level of PS I, another terminal component of the thylakoid electron transport system (ETS) was elevated, whereas it was lower under conditions where the level of PS I was reduced. Changes in the activity did not occur when protein synthesis was suppressed by chloramphenicol. The results suggest that, similarly to the regulation of levels of PS I, the activity or the amount of terminal oxidase in thylakoids is regulated in response to the redox steady-state of intermediate component(s) of ETS, in order to maintain a balance between the efflux of electrons from the ETS and the influx to the ETS.
日本植物生理学会の論文