Abstract
The ε subunit of ATP synthase has been suggested to function as an intrinsic inhibitor of ATPase activity, a regulator of ATP synthesis and a coupling factor. The ε subunit is comprised of N-terminal β sandwich domain and C-terminal helix-turn-helix domain, and the latter domain has been reported to be necessary for the inhibition of ATPase. To understand the physiological role of ε in the enzyme complex, we examined C-terminal truncation mutant of ε of Synechocystis sp. PCC 6803.
We confirmed that only the truncated ε was expressed in the mutant strain by immunoblot analysis. PAM measurement showed uncoupled photosynthetic electron transport activity. The ATPase activity of this mutant strain was higher than that of the wild-type when the assay was carried out using the isolated thylakoid membranes. In contrast, the mutant did not show any difference in growth from wild-type under low light, normal light and light/dark conditions.
