3.E.1.1.19
Glycylhalorhodopsins (GHR) of Salinarimonas soli of 263 aas and 7 TMSs (Ishizuka et al. 2024).  See 3.E.1.1.18 for details. This system transports anions including chloride and sulfate in the inward direction.  X-ray crystallographic analysis found large cavities on the cytoplasmic side, which are produced by the small side-chain volume of the glycine residue in the TTG motif in TMS3. The opened structure of GHR on the cytoplasmic side is probably related to the anion releasing process to the cytoplasm during the photoreaction compared to canonical halorhodopsin from Natronomonas pharaonis (NpHR). GHR also transports SO₄^2- and the extracellular glutamate residue plays an essential role in extracellular SO₄^2- uptake. Thus, Ishizuka et al. 2024 have identified a TTG motif-contained in microbial rhodopsins that may relate to an anion-releasing mechanism.