Discovery of a microbial rhodopsin that is the most stable in extreme environments

Abstract

Summary Microbial rhodopsin is a retinal protein that functions as an ion pump, channel, and sensory transducer, as well as a light sensor, as in biosensors and biochips. Tara76 rhodopsin is a typical proton-pumping rhodopsin that exhibits strong stability against extreme pH, detergent, temperature, salt stress, and dehydration stress and even under dual and triple conditions. Tara76 rhodopsin has a thermal stability approximately 20 times higher than that of thermal rhodopsin at 80°C and is even stable at 85°C. Tara76 rhodopsin is also stable at pH 0.02 to 13 and exhibits strong resistance in detergent, including Triton X-100 and SDS. We tested the current flow that electrical current flow across dried proteins on the paper at high temperatures using an electrode device, which was measured stably from 25°C up to 120°C. These properties suggest that this Tara76 rhodopsin is suitable for many applications in the fields of bioengineering and biotechnology.

Mutational analyses identify a single amino acid critical for colour tuning in proteorhodopsins

“…Based on their absorption maxima, PRs are classified into subgroups such as green‐light absorbing proteorhodopsin (GPR) and blue‐light absorbing proteorhodopsin (BPR) [24]. GPR and BPR have similar amino‐acid sequences (> 78%) but their maximum absorption wavelengths (λ max ) are 527 nm (green) and 490 nm (blue) at neutral pH respectively [19,22]. GPR and BPR have different photochemical properties based on their evolutionary and geographical features.…”

“…Biochemical studies of the functional differences of the acidic and alkaline states of PR have been performed [21]. In addition, the stability of PR-type rhodopsin was studied under stress such as high temperature and various conditions [22,23]. Studies on PRs are required to understand their biochemical characteristics and the evolution and geographical aspects of light [22].…”

“…GPR and BPR have similar amino-acid sequences (> 78%) but their maximum absorption wavelengths (k max ) are 527 nm (green) and Abbreviations BPR, blue-light absorbing proteorhodopsin; BR, bacteriorhodopsin; GPR, green-light absorbing proteorhodopsin; Ni-NTA, nickel-nitrilotriacetic acid; PR, proteorhodopsin. 490 nm (blue) at neutral pH respectively [19,22]. GPR and BPR have different photochemical properties based on their evolutionary and geographical features.…”

Rhodopsins: An Excitingly Versatile Protein Species for Research, Development and Creative Engineering

“…Likewise, the crystal structure of the thermostable rhodopsin proton-pump from Rubrobacter xylanophilus (RxR) is very similar to that of bacteriorhodopsin ( Hayashi et al, 2020 ). An unusually widely stable proton pump (pH, detergent, temperature), named Tara76 rhodopsin, was isolated from uncultured bacteria ( Shim et al, 2021 ). Such data shed new light on the design options to increase thermal and environmental stability without a significant sacrifice in dynamics and activity ( Hayashi et al, 2020 ).…”

“…Several concepts to utilize rhodopsins in bioelectronic and biomimic nanotechnology have already been attempted, but did not yet really come to maturation ( Khodonov et al, 2000 ; Kuang et al, 2014 ; Hirschi et al, 2019 ; Aprahamian, 2020 ; Shim et al, 2021 ). With the rapidly growing insight in the structural and mechanistic potential of the rhodopsin pigments, this is expected to change at short notice.…”