Disease relevance of hop

• Bacteriorhodopsin (BR) from Halobacterium salinarum as well as halorhodopsin (pHR) and sensory rhodopsin II (pSRII) from Natronobacterium pharaonis were functionally expressed in E. coli using the method of Shimono et al [1].

High impact information on hop

• In particular, the structure of pSRII exhibits a largely unbent conformation of the retinal (as compared with bacteriorhodopsin and halorhodopsin), a hydroxyl group of Thr-204 in the vicinity of the Schiff base, and an outward orientation of the guanidinium group of Arg-72 [2].
• Pharaonis halorhodopsin is a light-driven transport system for chloride, similarly to the previously described halorhodopsin, but we find that it transports nitrate as effectively as chloride [3].
• As expected from the lack of anion specificity in the transport, the photocycle of pharaonis halorhodopsin was nearly unaffected by replacement of chloride with nitrate [3].
• Peptide sequencing of cyanogen bromide fragments, and immunoreactions of the protein and synthetic peptides derived from the COOH-terminal gene sequence, confirmed that the open reading frame is the structural gene for the pharaonis halorhodopsin polypeptide [4].
• Halorhodopsin from Natronomonas pharaonis is a light-driven chloride pump which transports a chloride anion across the plasma membrane following light absorption by a retinal chromophore which initiates a photocycle [5].

Chemical compound and disease context of hop

• Purification of histidine tagged bacteriorhodopsin, pharaonis halorhodopsin and pharaonis sensory rhodopsin II functionally expressed in Escherichia coli [1].

Biological context of hop

• The subsequent reprotonation of the Schiff base is also dependent on azide, but with different kinetics that suggest a shuttling of protons from the surface as described earlier for halorhodopsin from Halobacterium salinarium [6].
• Light-driven chloride ion transport by halorhodopsin from Natronobacterium pharaonis. 1. The photochemical cycle [7].
• In halorhodopsin from Natronobacterium pharaonis, a light-driven chloride pump, the chloride binding site also binds azide [6].
• Photophosphorylation in alkalophilic halobacterial cells containing halorhodopsin: chloride-ion cycle [8]?

Anatomical context of hop

• Oriented gel samples were prepared from halorhodopsin-containing membranes from Natronobacterium pharaonis, and their photoelectric responses to laser flash excitation were measured at different chloride concentrations [9].

Associations of hop with chemical compounds

• In buffer containing nitrate, halorhodopsin exhibits a second, truncated photocycle; this difference in the photoreaction of the pigment occurs when an anion is bound in such a way as to preclude transport [3].
• Effect of anions on the photocycle of halorhodopsin. Substitution of chloride with formate anion [5].
• The uptake of chloride, bromide, iodide, nitrate, and azide by anion-depleted blue halorhodopsin from Natronobacterium pharaonis has been followed by FTIR difference spectroscopy using an ATR sampling device [10].
• Spin Labeling of Natronomonas pharaonis Halorhodopsin: Probing the Cysteine Residues Environment [11].
• These data can be explained if one suggests that halorhodopsin pumps C1- into the cells whereas C1- release from the cells through C1--ATP-synthase is coupled with the ATP synthesis (chloride-ion cycle) [8].

Analytical, diagnostic and therapeutic context of hop

• Anion Uptake in Halorhodopsin from Natromonas pharaonis Studied by FTIR Spectroscopy: Consequences for the Anion Transport Mechanism [10].
• Chromophore-anion interactions in halorhodopsin from Natronobacterium pharaonis probed by time-resolved resonance Raman spectroscopy [12].
• The photophobic receptor (psRII) and its transducer pHtrII from Natronobacterium pharaonis were heterologously coexpressed in the phototaxis-deficient Halobacterium salinarium strain Pho81/w which lacks all four bacterial rhodopsins, i.e. the two ion pumps bacteriorhodopsin and halorhodopsin as well as the two sensory pigments SRI and SRII [13].

References