FIG 6.

Proposed scenario for the regulation of atpT expression. Both the regulation of transcription and mRNA stability contribute to the atpT expression level. Two cyAbrBs bind to the promoter and 5’UTR of atpT, while the histone-like protein HU interacted mainly with the 5’UTR. Two AT-rich regions were identified in the atpT promoter that are relevant for regulation. These constitute HLR1 elements and bind RpaB. Multiple factors affect atpT expression, most prominently light/dark conditions or inhibition of electron transport by DCMU. The addition of glucose exerted two divergent effects: (i) a likely nonspecific stimulation of transcription and (ii) a substantially reduced atpT mRNA stability. The atpT gene product AtpΘ ultimately inhibits the ATP hydrolysis activity (reverse reaction) of F_oF₁ ATP synthase. As a third level of regulation, AtpΘ protein stability is dramatically reduced if cultures are transferred from the dark to light (17). The figure was drawn using BioRender (https://biorender.com/).