Multiple Roles of a Conserved Glutamate Residue for Unique Biophysical Properties in a New Group of Microbial Rhodopsins Homologous to TAT Rhodopsin.

Autor: Mannen K; The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan., Nagata T; The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan., Rozenberg A; Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel., Konno M; The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan., Del Carmen Marín M; The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan., Bagherzadeh R; The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan., Béjà O; Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel., Uchihashi T; Department of Physics, Nagoya University, Nagoya 464-8602, Japan; Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan; Institute for Glyco-core Research, Nagoya University, Nagoya 464-8602, Japan., Inoue K; The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan. Electronic address: inoue@issp.u-tokyo.ac.jp.
Jazyk: angličtina
Zdroj: Journal of molecular biology [J Mol Biol] 2024 Mar 01; Vol. 436 (5), pp. 168331. Date of Electronic Publication: 2023 Oct 26.
DOI: 10.1016/j.jmb.2023.168331
Abstrakt: TAT rhodopsin, a microbial rhodopsin found in the marine SAR11 bacterium HIMB114, uniquely possesses a Thr-Ala-Thr (TAT) motif in the third transmembrane helix. Because of a low pK a value of the retinal Schiff base (RSB), TAT rhodopsin exhibits both a visible light-absorbing state with the protonated RSB and a UV-absorbing state with the deprotonated RSB at a neutral pH. The UV-absorbing state, in contrast to the visible light-absorbing one, converts to a long-lived photointermediate upon light absorption, implying that TAT rhodopsin functions as a pH-dependent light sensor. Despite detailed biophysical characterization and mechanistic studies on the TAT rhodopsin, it has been unknown whether other proteins with similarly unusual features exist. Here, we identified several new rhodopsin genes homologous to the TAT rhodopsin of HIMB114 (TAT HIMB ) from metagenomic data. Based on the absorption spectra of expressed proteins from these genes with visible and UV peaks similar to that of TAT HIMB , they were classified as Twin-peaked Rhodopsin (TwR) family. TwR genes form a gene cluster with a set of 13 ORFs conserved in subclade IIIa of SAR11 bacteria. A glutamic acid in the second transmembrane helix, Glu54, is conserved in all of the TwRs. We investigated E54Q mutants of two TwRs and revealed that Glu54 plays critical roles in regulating the RSB pK a , oligomer formation, and the efficient photoreaction of the UV-absorbing state. The discovery of novel TwRs enables us to study the universality and individuality of the characteristics revealed so far in the original TAT HIMB and contributes to further studies on mechanisms of unique properties of TwRs.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 Elsevier Ltd. All rights reserved.)
Databáze: MEDLINE
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