Figure 2, 3, 4 data

<b>Figure 2: </b>Structural-based alteration of targeting mutants and the interaction of the retinal and carotenoid chromophores. (a) Maximum absorption shifted of targeted mutants. (b) The local view of mutation position shows in the red sphere Ser 221 for the strongest red-shifted and the blue sphere for Ser 181 for the strongest blue-shifted. (c) UV-vis spectra of wild type, S181G, and S221G. (d) Purified samples in 0.02% DDM. (e) Comparison of proton pumping with and without carotenoid, helix E mutants showed a reduction of proton pumping enhancement as a response to lower binding ration; however, helix F mutants with higher carotenoid binding ratio disrupted the benefit of carotenoid in proton pumping, suggesting the challenge of energy transfer and light absorption.