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Updated: May 15, 2026

Strategic Screening and Characterization of the Visual GPCR-mini-G Protein Signaling Complex for Successful Crystallization
Published on: March 16, 2020
Salt bridge in the conserved His-Asp cluster in Gloeobacter rhodopsin contributes to trimer formation
Takashi Tsukamoto1, Takashi Kikukawa, Takuro Kurata
1Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan.
Abstract:
Gloeobacter rhodopsin (GR) is a eubacterial proton pump having a highly conserved histidine near the retinal Schiff base counter-ion, aspartate. Various interactions between His and Asp of the eubacterial proton pump have been reported. Here, we showed the pH-dependent trimer/monomer transition of GR in the presence of dodecyl-β-D-maltoside by size-exclusion chromatography. The pH dependence was closely related to the protonation state of the counter-ion, Asp121. For the H87M mutant, pH dependence disappeared and a monomer became dominant. We concluded that the formation or breaking of the salt bridge between His87 and Asp121 inside the protein changes the quaternary structure.
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