Ktr-mediated potassium transport, a major pathway for potassium uptake, is coupled to a proton gradient across the membrane in Synechocystis sp. PCC 6803.

Synechocystis sp. PCC 6803 contains a Ktr system and a putative ATP-dependent Kdp system for potassium uptake. We report here that the Kdp system plays only a minor role in potassium uptake under salt and non-stress conditions, unlike the role it plays in Escherichia coli. In Synechocystis, Ktr-mediated potassium transport is dependent on the proton gradient across the membrane.