title: A novel six-rhodopsin system in a single archaeon.
abstract: Microbial rhodopsins, a diverse group of photoactive proteins found in Archaea, Bacteria, and Eukarya, function in photosensing and photoenergy harvesting and may have been present in the resource-limited early global environment. Four different physiological functions have been identified and characterized for nearly 5,000 retinal-binding photoreceptors, these being ion transporters that transport proton or chloride and sensory rhodopsins that mediate light-attractant and/or -repellent responses. The greatest number of rhodopsins previously observed in a single archaeon had been four. Here, we report a newly discovered six-rhodopsin system in a single archaeon, Haloarcula marismortui, which shows a more diverse absorbance spectral distribution than any previously known rhodopsin system, and, for the first time, two light-driven proton transporters that respond to the same wavelength. All six rhodopsins, the greatest number ever identified in a single archaeon, were first shown to be expressed in H. marismortui, and these were then overexpressed in Escherichia coli. The proteins were purified for absorption spectra and photocycle determination, followed by measurement of ion transportation and phototaxis. The results clearly indicate the existence of a proton transporter system with two isochromatic rhodopsins and a new type of sensory rhodopsin-like transducer in H. marismortui.
authors.affiliation: Institute of Microbiology and Biochemistry, National Taiwan University, Taipei, Taiwan.
authors.forename: Hsu-Yuan
authors.initials: HY
authors.lastname: Fu
authors.forename: Yu-Cheng
authors.initials: YC
authors.lastname: Lin
authors.forename: Yung-Ning
authors.initials: YN
authors.lastname: Chang
authors.forename: Hsiaochu
authors.initials: H
authors.lastname: Tseng
authors.forename: Ching-Che
authors.initials: CC
authors.lastname: Huang
authors.forename: Kang-Cheng
authors.initials: KC
authors.lastname: Liu
authors.forename: Ching-Shin
authors.initials: CS
authors.lastname: Huang
authors.forename: Che-Wei
authors.initials: CW
authors.lastname: Su
authors.forename: Rueyhung Roc
authors.initials: RR
authors.lastname: Weng
authors.forename: Yin-Yu
authors.initials: YY
authors.lastname: Lee
authors.forename: Wailap Victor
authors.initials: WV
authors.lastname: Ng
authors.forename: Chii-Shen
authors.initials: CS
authors.lastname: Yang
mesh_terms: D019843:Archaeal Proteins / Q000235:genetics*; D001692:Biological Transport; D003001:Cloning, Molecular; D004926:Escherichia coli; D015870:Gene Expression; D020869:Gene Expression Profiling; D019614:Haloarcula marismortui / Q000235:genetics / Q000502:physiology*; D008027:Light; D009068:Movement; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013057:Spectrum Analysis
chemical_list: D019843:Archaeal Proteins; D011994:Recombinant Proteins; D012243:Rhodopsin
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