Masae Konno

The University of Tokyo | Todai · Department of Frontier Materials

Microbial rhodopsins are photoreceptive transmembrane proteins that transport ions or regulate other intracellular biological processes. Recent genomic and metagenomic analyses found many microbial rhodopsins with unique sequences distinct from known ones. Functional characterization of these new types of microbial rhodopsins is expected to expand...

Energy transfer from light-harvesting ketocarotenoids to the light-driven proton pump xanthorhodopsins has been previously demonstrated in two unique cases: an extreme halophilic bacterium¹ and a terrestrial cyanobacterium². Attempts to find carotenoids that bind and transfer energy to abundant rhodopsin proton pumps³ from marine photoheterotrophs...

The KCR channelrhodopsins are recently-discovered light-gated ion channels with high K ⁺ selectivity, a property that has attracted broad attention among biologists– due to intense interest in creating novel inhibitory tools for optogenetics leveraging this K ⁺ selectivity, and due to the mystery of how this selectivity is achieved in the first pla...

Rhodopsins convert light into signals and energy in animals and microbes. Heliorhodopsins (HeRs), a recently discovered new rhodopsin family, are widely present in archaea, bacteria, unicellular eukaryotes, and giant viruses, but their function remains unknown. Here, we report that a viral HeR from Emiliania huxleyi virus 202 (V2HeR3) is a light-ac...

Energy transfer from light-harvesting ketocarotenoids to light-driven proton pumps xanthorhodopsins has been previously demonstrated in two unique cases: an extreme halophilic bacterium and a terrestrial cyanobacterium. Attempts to find carotenoids that bind and transfer energy to rhodopsin proton pumps from the abundant marine and freshwater photo...

Schizorhodopsins (SzRs) are light-driven inward proton pumping membrane proteins. A H⁺ is released to the cytoplasmic solvent from the chromophore, retinal Schiff base (RSB), after light absorption, and then another H⁺ is bound to the RSB at the end of photocyclic reaction. However, the mechanistic detail of H⁺ transfers in SzR is almost unknown. H...

Many organisms sense light using rhodopsins, photoreceptive proteins containing a retinal chromophore. Here we report the discovery, structure and biophysical characterization of bestrhodopsins, a microbial rhodopsin subfamily from marine unicellular algae, in which one rhodopsin domain of eight transmembrane helices or, more often, two such domain...

Microbial rhodopsins are a family of photoreceptive membrane proteins with a wide distribution across the Tree of Life. Within the candidate phyla radiation (CPR), a diverse group of putatively episymbiotic bacteria, the genetic potential to produce rhodopsins appears to be confined to a small clade of organisms from sunlit environments. Here, we c...

Rhodopsins convert light into signals and energy in animals and microbes. Heliorhodopsins (HeRs), a recently discovered new rhodopsin family, are widely present in archaea, bacteria, unicellular eukaryotes, and giant viruses, but their function remains unknown. Here we report that a viral HeR from Emiliania huxleyi virus 202 (V2HeR3) is a light-gat...

Microbial rhodopsins are a family of photoreceptive membrane proteins with a wide distribution across the Tree of Life. Within the Candidate Phyla Radiation (CPR), a diverse group of putatively episymbiotic bacteria, the genetic potential to produce rhodopsins appears to be confined to a small clade of organisms from sunlit environments. Here, we c...

ChRmine, a recently discovered pump-like cation-conducting channelrhodopsin, exhibits puzzling properties (large photocurrents, red-shifted spectrum, and extreme light sensitivity) that have created new opportunities in optogenetics. ChRmine and its homologs function as ion channels but, by primary sequence, more closely resemble ion pump rhodopsin...

DTG/DTS rhodopsin, which was named based on a three-residue motif (DTG or DTS) that is important for its function, is a light-driven proton-pumping microbial rhodopsin using a retinal chromophore. In contrast to other light-driven ion-pumping rhodopsins, DTG/DTS rhodopsin does not have a cytoplasmic proton donor residue such as Asp, Glu, or Lys. Be...

ChRmine, a recently-discovered bacteriorhodopsin-like cation-conducting channelrhodopsin, exhibits puzzling properties (unusually-large photocurrents, exceptional red-shift in action spectrum, and extreme light-sensitivity) that have opened up new opportunities in optogenetics. ChRmine and its homologs function as light-gated ion channels, but by p...

Microbial rhodopsins have diverse functions, including roles as light-driven ion pumps, light-gated ion channels, photosensors, and light-regulated enzymes. As the number of rhodopsin-like genes identified has increased in recent years, so has the requirement for rapid identification of their functions. The patch-clamp method is often used to inves...

Schizorhodopsins (SzR), a sub-family of microbial rhodopsin, are light-driven inward proton pumps using a retinal chromophore. Here, we studied new SzRs, MtSzR and MsSzR, from methanogenic archaea (genus Methanoculleus) reported as mesophilic and sampled at a hot spring, respectively. While MtSzR and MsSzR exhibited light-driven inward proton trans...

Significance We present a high-resolution structure of schizorhodopsin (SzR), a new rhodopsin family identified in Asgard archaea. SzRs work as light-driven inward H ⁺ pumps as bacterial xenorhodopsins. Although SzRs are phylogenetically located at an intermediate position between type-1 microbial rhodopsins and heliorhodopsins, the structure of Sz...

Microbial rhodopsins are photoreceptive membrane proteins, which are used as molecular tools in optogenetics. Here, a machine learning (ML)-based experimental design method is introduced for screening rhodopsins that are likely to be red-shifted from representative rhodopsins in the same subfamily. Among 3,022 ion-pumping rhodopsins that were sugge...

The Cryptomonad Guillardia theta has 42 genes encoding microbial rhodopsin-like proteins in their genomes. Light-driven ion-pump activity has been reported for some rhodopsins based on heterologous E . coli or mammalian cell expression systems. However, neither their physiological roles nor the expression of those genes in native cells are known. T...

Schizorhodopsins (SzRs), a new rhodopsin family identified in Asgard archaea, are phylogenetically located at an intermediate position between type-1 microbial rhodopsins and heliorhodopsins. SzRs reportedly work as light-driven inward H+ pumps, as xenorhodopsin. Here we report the crystal structure of SzR AM_5_00977 at 2.1 angstrom resolution. The...

Microbial rhodopsins are photoreceptive membrane proteins utilized as molecular tools in optogenetics. In this paper, a machine learning (ML)-based model was constructed to approximate the relationship between amino acid sequences and absorption wavelengths using ≈800 rhodopsins with known absorption wavelengths. This ML-based model was specificall...

Schizorhodopsins (SzRs), a rhodopsin family first identified in Asgard archaea, the archaeal group closest to eukaryotes, are present at a phylogenetically intermediate position between typical microbial rhodopsins and heliorhodopsins. However, the biological function and molecular properties of SzRs have not been reported. Here, SzRs from Asgardar...

Heliorhodopsins (HeRs) are a family of rhodopsins that was recently discovered using functional metagenomics¹. They are widely present in bacteria, archaea, algae and algal viruses2,3. Although HeRs have seven predicted transmembrane helices and an all-trans retinal chromophore as in the type-1 (microbial) rhodopsin, they display less than 15% sequ...

Definition of rhodopsin is the retinal‐binding membrane protein with the Schiff base linkage at a lysine on the 7th transmembrane helix. However, ~ 600 microbial rhodopsins lack retinal‐binding lysine at the corresponding position (Rh‐noK) among ~ 5,500 known microbial rhodopsins, suggesting that Rh‐noK has each functional role without chromophore....

Many organisms capture or sense sunlight using rhodopsin pigments1,2, which are integral membrane proteins that bind retinal chromophores. Rhodopsins comprise two distinct protein families 1 , type-1 (microbial rhodopsins) and type-2 (animal rhodopsins). The two families share similar topologies and contain seven transmembrane helices that form a p...

Oligomeric assembly is a common feature of membrane proteins and often relevant to their physiological functions. Determining the stoichiometry and the oligomeric state of membrane proteins in a lipid bilayer is generally challenging because of their large size, complexity, and structural alterations under experimental conditions. Here, we use high...

Microbial rhodopsins are membrane proteins found widely in archaea, eubacteria and eukaryotes (fungal and algal species). They have various functions, such as light-driven ion pumps, light-gated ion channels, light sensors and light-activated enzymes. A light-driven proton pump bacteriorhodopsin (BR) contains a DTD motif at positions 85, 89, and 96...

Krokinobacter eikastus rhodopsin 2 (KR2) is a light-driven Na+ pump found in marine bacterium. KR2 pumps Li+ and Na+, but it becomes an H+ pump in the presence of K+, Rb+, and Cs+. Site-directed mutagenesis of the cytoplasmic surface successfully converted KR2 into a light-driven K+ pump, suggesting that ion selectivity is determined at the cytopla...

Sodium-pumping rhodopsins (NaRs) are light-driven outward Na(+) pumps. NaRs have a conserved Asn, Asp, and Gln motif (NDQ) in the third transmembrane helix (helix C). The NDQ motif is thus expected to play a crucial role in the operation of the Na(+) pump. Herein, we studied the photocycles of the NDQ-motif mutants of Krokinobacter rhodopsin 2 (KR2...

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Krokinobacter eikastus rhodopsin 2 (KR2) is the first light-driven Na(+) pump discovered, and is viewed as a potential next-generation optogenetics tool. Since the positively charged Schiff base proton, located within the ion-conducting pathway of all light-driven ion pumps, was thought to prohibit the transport of a non-proton cation, the discover...

Elevated CO2 concentrations (eCO2) trigger various plant responses. Despite intensive studies of these responses, the underlying mechanisms remain obscure. In this work, we investigated when and how leaf physiology and anatomy are affected by eCO2 in rice plants. We analyzed the most recently fully expanded leaves that developed successively after...

A new bio-imaging sensor with photosystem I (PSI) of Thermosynechococcus elongatus and complementary metal-oxide-semiconductor (CMOS) circuits is demonstrated. Photons are converted into electrons by PSI, and electrons are detected as an electric signal by a CMOS integrated circuit. For a sensor circuit, a 4 × 4 sensor array with a CMOS source-drai...

Photosensing performance of a system composed of photosystem I (PSI), vitamin K(1) (VK(1))-like molecular wire, and gold nanoparticles (AuNPs) in an aqueous solution was increased considerably by the addition of double surfactants, hexylamine and dodecylbenzenesulfonate.

A new bio-photosensor where photons are converted to electrons by photosystem I (PSI) of Thermosynechococcus elongatus is described; in this bio-photosensor, the converted electronic charge is sensed by a complementary metal-oxide-semiconductor (CMOS) source-drain follower circuit fabricated by the 1.2 mum standard CMOS process. Thin Au/Ti films ar...

We have investigated a photosensor that consists of a field emission transistor (FET) utilizing the biocomponent of the photosystem I (PSI) protein complex for use in an imaging device. The PSI was immobilized on a gold electrode via the self-assembling monolayer (SAM) of 3-mercapto-1-propanesulfonic acid sodium salt to obtain a PSI-modified gold e...

We present a bio-photoelectrode made of photosystem I complex (PSI) of cyanobacteria, Thermosynechococcus elongatus, and molecular wires. The newly designed and synthesized molecular wire similar to vitamin K1 (VK1) has a naphthoquinone moiety that can connect to PSI, and a terpyridine moiety for connection to a Co(II) ion. Surface immobilization o...

Root hairs, which arise from root epidermal cells, are tubular structures that increase the efficiency of water absorption and nutrient uptake. A low pH (pH 4) medium induced root hair formation in lettuce (Lactuca sativa L.) seedlings, and the decapitation of shoots inhibited root hair formation. The addition of shoot extract to the medium restore...

We investigated whether low-pH-induced manganese (Mn) deficiency causes low-pH-induced root hair formation in lettuce seedlings. Both the number and length of root hairs increased in 0 microM Mn (Mn-free) at pH 6 and decreased in 3 mM Mn (excess Mn) at pH 4 compared with the values in 10 microM Mn (normal Mn). These results indicate an inhibitory e...

Root hair formation is induced by low pH in lettuce ( Lactuca sativa L. cv. Grand Rapids) seedlings cultured in mineral medium. The role of mineral concentrations in this phenomenon was investigated, especially for manganese. When lettuce seedlings were cultured in media that were deficient in calcium (Ca), manganese (Mn), boron (B) or molybdenum (...