Premium
In Situ Study of the Function of Bacterioruberin in the Dual‐Chromophore Photoreceptor Archaerhodopsin‐4
Author(s) -
Sun Chao,
Ding Xiaoyan,
Cui Haolin,
Yang Yanan,
Chen Sijin,
Watts Anthony,
Zhao Xin
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201803195
Subject(s) - chromophore , retinal , chemistry , biophysics , ligand (biochemistry) , stereochemistry , receptor , crystallography , photochemistry , biochemistry , biology
While certain archaeal ion pumps have been shown to contain two chromophores, retinal and the carotenoid bacterioruberin, the functions of bacterioruberin have not been well explored. To address this research gap, recombinant archaerhodopsin‐4 (aR4), either with retinal only or with both retinal and bacterioruberin chromophores, was successfully expressed together with endogenous lipids in H. salinarum L33 and MPK409 respectively. In situ solid‐state NMR, supported by molecular spectroscopy and functional assays, revealed for the first time that the retinal thermal equilibrium in the dark‐adapted state is modulated by bacterioruberin binding through a cluster of aromatic residues on helix E. Bacterioruberin not only stabilizes the protein trimeric structure but also affects the photocycle kinetics and the ATP formation rate. These new insights may be generalized to other receptors and proteins in which metastable thermal equilibria and functions are perturbed by ligand binding.