3.E.1.1.13
Xenorhodopsinof 229 aas and 7 TMSs.  The structures have been determined for all intermediates of the photocycle;  7ZNB, C, D, E, G, H and I, all A - C. Thus, a comprehensive function-structure study of the light-driven bacterial inward proton pump, xenorhodopsin from Bacillus coahuilensis, in all major proton-conducting states was carried out (Kovalev et al. 2023). The structures revealed that proton translocation is based on proton wires regulated by internal gates. The wires serve as both selectivity filters and the translocation pathways for protons. The cumulative results suggest a general concept of proton translocation. Kovalev et al. 2023 demonstrated the use of serial time-resolved crystallography at a synchrotron source with sub-millisecond resolution for rhodopsin studies, opening the door for principally new applications.