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Updated: Jan 25, 2026

A Rhodopsin Transport Assay by High-Content Imaging Analysis
Published on: January 16, 2019
Engineered Functional Recovery of Microbial Rhodopsin Without Retinal-Binding Lysine
Yumeka Yamauchi1, Masae Konno1,2, Daichi Yamada1
1Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Aichi, Japan.
Abstract:
Definition of rhodopsin is the retinal-binding membrane protein with the Schiff base linkage at a lysine on the 7th transmembrane helix. However, ~ 600 microbial rhodopsins lack retinal-binding lysine at the corresponding position (Rh-noK) among ~ 5500 known microbial rhodopsins, suggesting that Rh-noK has each functional role without chromophore. Here, we report successful functional recovery of Rh-noK. Two Rh-noKs from bacteria were heterologously expressed in Escherichia coli, which exhibited no color. When retinal-binding lysine was introduced, one of them gained visible color. Additional mutation of the Schiff base counterion further gained proton-pumping activity. Successful engineered functional recovery such as visible color and proton-pump activity suggests that the Rh-noK protein forms a characteristic structure of microbial rhodopsins.
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