Dataset Information

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 (?max 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.

SUBMITTER: Ganapathy S

PROVIDER: S-EPMC6849744 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Redshifted and Near-infrared Active Analog Pigments Based upon Archaerhodopsin-3.

Ganapathy Srividya S Kratz Svenja S Chen Que Q Hellingwerf Klaas J KJ de Groot Huub J M HJM Rothschild Kenneth J KJ de Grip Willem J WJ

Photochemistry and photobiology 20190408 4

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 (λmax 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 transmemb ...[more]

PMID: 30860604

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Project description:Archaerhodopsin 3 (AR3) is a light driven proton pump from Halorubrum sodomense that has been used as a genetically targetable neuronal silencer and an effective fluorescent sensor of transmembrane potential. Unlike the more extensively studied bacteriorhodopsin (BR) from Halobacterium salinarum, AR3 readily incorporates into the plasma membrane of both E. coli and mammalian cells. Here, we used near-IR resonance Raman confocal microscopy to study the effects of pH and membrane potential on the AR3 retinal chromophore structure. Measurements were performed both on AR3 reconstituted into E. coli polar lipids and in vivo in E. coli expressing AR3 in the absence and presence of a negative transmembrane potential. The retinal chromophore structure of AR3 is in an all-trans configuration almost identical to BR over the entire pH range from 3 to 11. Small changes are detected in the retinal ethylenic stretching frequency and Schiff Base (SB) hydrogen bonding strength relative to BR which may be related to a different water structure near the SB. In the case of the AR3 mutant D95N, at neutral pH an all-trans retinal O-like species (O(all-trans)) is found. At higher pH a second 13-cis retinal N-like species (N(13-cis)) is detected which is attributed to a slowly decaying intermediate in the red-light photocycle of D95N. However, the amount of N(13-cis) detected is less in E. coli cells but is restored upon addition of carbonyl cyanide m-chlorophenyl hydrazone (CCCP) or sonication, both of which dissipate the normal negative membrane potential. We postulate that these changes are due to the effect of membrane potential on the N(13-cis) to M(13-cis) levels accumulated in the D95N red-light photocycle and on a molecular level by the effects of the electric field on the protonation/deprotonation of the cytoplasmic accessible SB. This mechanism also provides a possible explanation for the observed fluorescence dependence of AR3 and other microbial rhodopsins on transmembrane potential.

Dataset Information

Redshifted and Near-infrared Active Analog Pigments Based upon Archaerhodopsin-3.

Publications

Redshifted and Near-infrared Active Analog Pigments Based upon Archaerhodopsin-3.

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