Redshifted and Near‐infrared Active Analog Pigments Based upon Archaerhodopsin‐3

Abstract

Archaerhodopsin-3 (AR3) is a member of the microbial rhodopsin family of hepta-helical transmembrane proteins, containing a covalently bound molecule of all-trans retinal as a chromophore. It displays an absorbance band in the visible region of the solar spectrum (kmax 556 nm) and functions as a light-driven proton pump in the archaeon Halorubrum sodomense. AR3 and its mutants are widely used in neuroscience as optogenetic neural silencers and in particular as fluorescent indicators of transmembrane potential. In this study, we investigated the effect of analogs of the native ligand all-trans retinal A1 on the spectral properties and proton-pumping activity of AR3 and its single mutant AR3 (F229S). While, surprisingly, the 3-methoxyretinal A2 analog did not redshift the absorbance maximum of AR3, the analogs retinal A2 and 3-methylamino-16-nor-1,2,3,4-didehydroretinal (MMAR) did generate active redshifted AR3 pigments. The MMAR analog pigments could even be activated by near-infrared light. Furthermore, the MMAR pigments showed strongly enhanced fluorescence with an emission band in the near-infrared peaking around 815 nm. We anticipate that the AR3 pigments generated in this study have widespread potential for near-infrared exploitation as fluorescent voltage-gated sensors in optogenetics and artificial leafs and as proton pumps in bioenergy-based applications.

Toward Artificial Cells: Novel Advances in Energy Conversion and Cellular Motility

“…Proton‐Gradient‐Driven ATP Synthesis : Proton pumps on a membrane can be activated by using various sources of energy, such as energy derived from electron transport, hydrolysis of inorganic pyrophosphate, or light . As a proton goes through ATP synthase, which works as a proton pump, it converts ADP into ATP, and the resulting energy is subsequently stored in the high‐energy phosphate bond of ATP until it is needed for further reactions .…”

Genomic and transcriptomic evidence of light-sensing, porphyrin biosynthesis, Calvin-Benson-Bassham cycle, and urea production in Bathyarchaeota

“…However, previous studies have revealed that most of bathyarchaeotal members prefer subsurface of the sediments and large numbers of Bathyarchaeota were found in deeper biosphere where visible light could barely reach [6,18,22,30], thus Bathyarchaeota may not capture visible light with rhodopsin. Infrared light has been proved to be an available energy source for some plants and bacteria [31][32][33][34][35], and rhodopsin could gain longerwavelength or even infrared sensitivity by substituting all-trans-retinal (chromophore for archaeal cells) with 3, 4-dehydroretinal [36], retinal A2, 3-methylamino-16nor-1,2,3,4-didehydroretinal, or other analogs [37].…”

Spectral and Thermal Properties of Rhodopsins: Closely Related but not Tightly Coupled

“…630 nm found in nature stable enough to be useful? On a different track, it is interesting to follow the engineering of microbial ("type 1") rhodopsins with the purpose of developing improved tools for optogenetics, for example, by moving their spectral absorbance further into the infrared [84][85][86][87]. Values for all of these can be derived from electrophysiological experiments on the light-sensitive current of photoreceptor cells.…”