Limits...
Ion-pumping microbial rhodopsins.

Kandori H - Front Mol Biosci (2015)

Bottom Line: Ion-transporting proteins can be found in microbial rhodopsins, such as light-gated channels and light-driven pumps, which are the main tools in optogenetics.On the other hand, different kinds of H(+) and Cl(-) pumps have been found in marine bacteria, such as proteorhodopsin (PR) and Fulvimarina pelagi rhodopsin (FR), respectively.In addition, a light-driven Na(+) pump was found, Krokinobacter eikastus rhodopsin 2 (KR2).

View Article: PubMed Central - PubMed

Affiliation: Department of Frontier Materials and OptoBioTechnology Research Center, Nagoya Institute of Technology Nagoya, Japan.

ABSTRACT
Rhodopsins are light-sensing proteins used in optogenetics. The word "rhodopsin" originates from the Greek words "rhodo" and "opsis," indicating rose and sight, respectively. Although the classical meaning of rhodopsin is the red-colored pigment in our eyes, the modern meaning of rhodopsin encompasses photoactive proteins containing a retinal chromophore in animals and microbes. Animal and microbial rhodopsins possess 11-cis and all-trans retinal, respectively, to capture light in seven transmembrane α-helices, and photoisomerizations into all-trans and 13-cis forms, respectively, initiate each function. Ion-transporting proteins can be found in microbial rhodopsins, such as light-gated channels and light-driven pumps, which are the main tools in optogenetics. Light-driven pumps, such as archaeal H(+) pump bacteriorhodopsin (BR) and Cl(-) pump halorhodopsin (HR), were discovered in the 1970s, and their mechanism has been extensively studied. On the other hand, different kinds of H(+) and Cl(-) pumps have been found in marine bacteria, such as proteorhodopsin (PR) and Fulvimarina pelagi rhodopsin (FR), respectively. In addition, a light-driven Na(+) pump was found, Krokinobacter eikastus rhodopsin 2 (KR2). These light-driven ion-pumping microbial rhodopsins are classified as DTD, TSA, DTE, NTQ, and NDQ rhodopsins for BR, HR, PR, FR, and KR2, respectively. Recent understanding of ion-pumping microbial rhodopsins is reviewed in this paper.

No MeSH data available.


Schematic drawing of alternative access in BR.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4585134&req=5

Figure 10: Schematic drawing of alternative access in BR.

Mentions: If the Schiff base of M is reprotonated from D85 in BR (the first D in DTD), no H+ transport occurs. In reality, the Schiff base is reprotonated from D96 (the last D in DTD) in the cytoplasmic region (Figures 6, 8), by which the N intermediate is formed (Gerwert et al., 1989). The molecular mechanism of unidirectional transport of H+s in BR has attracted the attention of many researchers, and it is believed that the primary H+ transfer from the Schiff base to D85, and the subsequent H+ transfer from D96 to the Schiff base determine the unidirectionality from the cytoplasmic to the extracellular region. The crystal structure of BR exhibits an asymmetric pattern of hydration: while seven internal water molecules are found in the extracellular half, only two are observed in the cytoplasmic half (Figure 10). Such asymmetry makes sense in view of BR's function, as the water molecules build a hydrogen-bonding network on the extracellular side for fast H+ release while the cytoplasmic side is likely inaccessible in the dark and allows H+ uptake only after the light-induced accessibility switch. Such asymmetric access (EC open and CP closed) is not only the case for the unphotolyzed state, but is also the case for the K and M intermediates, as shown in Figure 9.


Ion-pumping microbial rhodopsins.

Kandori H - Front Mol Biosci (2015)

Schematic drawing of alternative access in BR.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585134&req=5

Figure 10: Schematic drawing of alternative access in BR.
Mentions: If the Schiff base of M is reprotonated from D85 in BR (the first D in DTD), no H+ transport occurs. In reality, the Schiff base is reprotonated from D96 (the last D in DTD) in the cytoplasmic region (Figures 6, 8), by which the N intermediate is formed (Gerwert et al., 1989). The molecular mechanism of unidirectional transport of H+s in BR has attracted the attention of many researchers, and it is believed that the primary H+ transfer from the Schiff base to D85, and the subsequent H+ transfer from D96 to the Schiff base determine the unidirectionality from the cytoplasmic to the extracellular region. The crystal structure of BR exhibits an asymmetric pattern of hydration: while seven internal water molecules are found in the extracellular half, only two are observed in the cytoplasmic half (Figure 10). Such asymmetry makes sense in view of BR's function, as the water molecules build a hydrogen-bonding network on the extracellular side for fast H+ release while the cytoplasmic side is likely inaccessible in the dark and allows H+ uptake only after the light-induced accessibility switch. Such asymmetric access (EC open and CP closed) is not only the case for the unphotolyzed state, but is also the case for the K and M intermediates, as shown in Figure 9.

Bottom Line: Ion-transporting proteins can be found in microbial rhodopsins, such as light-gated channels and light-driven pumps, which are the main tools in optogenetics.On the other hand, different kinds of H(+) and Cl(-) pumps have been found in marine bacteria, such as proteorhodopsin (PR) and Fulvimarina pelagi rhodopsin (FR), respectively.In addition, a light-driven Na(+) pump was found, Krokinobacter eikastus rhodopsin 2 (KR2).

View Article: PubMed Central - PubMed

Affiliation: Department of Frontier Materials and OptoBioTechnology Research Center, Nagoya Institute of Technology Nagoya, Japan.

ABSTRACT
Rhodopsins are light-sensing proteins used in optogenetics. The word "rhodopsin" originates from the Greek words "rhodo" and "opsis," indicating rose and sight, respectively. Although the classical meaning of rhodopsin is the red-colored pigment in our eyes, the modern meaning of rhodopsin encompasses photoactive proteins containing a retinal chromophore in animals and microbes. Animal and microbial rhodopsins possess 11-cis and all-trans retinal, respectively, to capture light in seven transmembrane α-helices, and photoisomerizations into all-trans and 13-cis forms, respectively, initiate each function. Ion-transporting proteins can be found in microbial rhodopsins, such as light-gated channels and light-driven pumps, which are the main tools in optogenetics. Light-driven pumps, such as archaeal H(+) pump bacteriorhodopsin (BR) and Cl(-) pump halorhodopsin (HR), were discovered in the 1970s, and their mechanism has been extensively studied. On the other hand, different kinds of H(+) and Cl(-) pumps have been found in marine bacteria, such as proteorhodopsin (PR) and Fulvimarina pelagi rhodopsin (FR), respectively. In addition, a light-driven Na(+) pump was found, Krokinobacter eikastus rhodopsin 2 (KR2). These light-driven ion-pumping microbial rhodopsins are classified as DTD, TSA, DTE, NTQ, and NDQ rhodopsins for BR, HR, PR, FR, and KR2, respectively. Recent understanding of ion-pumping microbial rhodopsins is reviewed in this paper.

No MeSH data available.