Figure 2: Light-driven proton and sodium ion transport by KR1 and KR2.

(a) Absorption spectra of purified KR1 and KR2 solubilized in the detergent DDM. (b) Pump activity of E. coli cell suspensions in 100 mM NaCl expressing KR1 without (blue) and with (green) CCCP. (c) Pump activity of E. coli cell suspensions in 100 mM NaCl expressing KR2. The activities after additions of CCCP (green) and CCCP+TPP⁺ (orange) are shown. (d) Light-induced pump activity of E. coli cell suspensions (100 mM) of different salt solutions expressing KR2. The activities after additions of CCCP (dashed lines) and CCCP+TPP⁺ (dotted lines) are shown.