Related Experiment Video
Updated: Mar 6, 2026
13:40
In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa
Published on: February 17, 2014
12.3K
A phylogenetically distinctive and extremely heat stable light-driven proton pump from the eubacterium Rubrobacter
Kanae Kanehara1, Susumu Yoshizawa2, Takashi Tsukamoto1,3
1Division of Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan.
Scientific Reports
|March 15, 2017
Summary
A novel rhodopsin from the thermophilic bacterium Rubrobacter xylanophilus, named RxR, functions as a light-driven proton pump. This unique rhodopsin exhibits exceptional thermal stability, surpassing other known proton pumps.
Area of Science:
- Biochemistry
- Microbiology
- Structural Biology
Background:
- Rhodopsins are essential photoreceptor proteins found across diverse organisms.
- They play critical roles in light-energy conversion and signal transduction.
- A novel rhodopsin from the thermophilic bacterium Rubrobacter xylanophilus (RxR) was investigated.
Purpose of the Study:
- To characterize a phylogenetically distinct rhodopsin from Rubrobacter xylanophilus.
- To elucidate the functional mechanism and properties of this new rhodopsin.
- To assess its thermal stability compared to other rhodopsins.
Main Methods:
- Phylogenetic analysis of the rhodopsin.
- Functional characterization in E. coli expressing RxR, including pH measurements.
- Spectroscopic analysis of purified RxR, including absorption maxima and retinal binding.
- Time-resolved flash-photolysis experiments.
- Thermal stability assays.
Main Results:
- RxR functions as a light-driven outward proton pump, evidenced by pH decrease and protonophore inhibition.
- Purified RxR exhibits an absorption maximum at 541 nm and binds all-trans retinal.
- Estimated pKa values for the protonated retinal Schiff base and its counterion are 10.7 and 1.3, respectively.
- Time-resolved studies indicated a red-shifted intermediate.
- RxR demonstrated significantly higher thermal stability than thermophilic rhodopsin TR and Halobacterium salinarum bacteriorhodopsin (HsBR).
Conclusions:
- The novel rhodopsin RxR from Rubrobacter xylanophilus is a functional light-driven proton pump.
- RxR possesses unique phylogenetic placement and remarkable thermal stability.
- These findings expand our understanding of rhodopsin diversity and function in extreme environments.
Related Concept Videos
01:21Hyperthermophilic Bacteria
652
Domain Bacteria includes some unique hyperthermophilic species. They exhibit remarkable adaptations that enable survival in extreme environments.Thermotoga species are rod-shaped, gram-negative, non-sporulating hyperthermophiles that form a sheath-like envelope called a toga. They ferment sugars or starch, producing lactate, acetate, CO₂, and H₂, and can also grow via anaerobic respiration using H₂ and ferric iron. Found in hot springs and hydrothermal vents, over 20% of their...
652
01:28Anoxygenic Phototrophic Bacteria
1.0K
Anoxygenic phototrophic bacteria are a diverse group of microorganisms that perform photosynthesis without producing oxygen. They primarily include purple sulfur bacteria, purple nonsulfur bacteria, green sulfur bacteria, and green nonsulfur bacteria. These bacteria are classified into the Gammaproteobacteria, Alphaproteobacteria, Betaproteobacteria, Chlorobi, and Chloroflexi lineages, each with distinct physiological and ecological adaptations.Purple sulfur bacteria belong to the...
1.0K
01:30Anoxygenic Photosynthesis
1.5K
Anoxygenic photosynthesis is a phototrophic process that captures light energy to drive carbon fixation without producing molecular oxygen. Unlike oxygenic photosynthesis, which utilizes water as an electron donor and releases oxygen, anoxygenic phototrophs use alternative electron donors such as hydrogen sulfide (H₂S), elemental sulfur (S⁰), or thiosulfate (S₂O₃²⁻). This process is carried out by diverse groups of bacteria, including purple bacteria, green...
1.5K
01:27Diversity of Archaea III
406
Crenarchaeota, a prominent phylum of Archaea, is remarkable for its ability to thrive in extreme environments characterized by high temperatures and acidity. These microorganisms inhabit sulfuric hot springs, volcanic systems, and submarine hydrothermal vents, where temperatures often exceed 100°C. The unique adaptations of Crenarchaeota not only allow survival under such extreme conditions but also provide insights into the mechanisms of life in primordial Earth-like...
406
01:29Diversity of Archaea IV
563
Hyperthermophilic archaea are a group of extremophiles thriving at temperatures above 80°C, often in hydrothermal vents and volcanic soils where conditions surpass the boiling point of water. At such temperatures, proteins, membranes, and DNA in most organisms degrade, but hyperthermophiles have evolved remarkable adaptations to maintain stability and function.Unique Cellular FeaturesHyperthermophilic membranes are composed of a monolayer of biphytanyl tetraether lipids, which resist...
563
01:29Electron Transport Chain Components
1.1K
The electron transport chain (ETC) is a crucial metabolic pathway that facilitates energy conversion in prokaryotic and eukaryotic cells. In eukaryotes, the ETC comprises four membrane-associated protein complexes in the inner mitochondrial membrane. In prokaryotes, the ETC in the plasma membrane can vary in composition, with fewer or different complexes depending on the organism and environmental conditions. These complexes transfer electrons from electron donors, such as NADH and FADH2, to...
1.1K