| Spectroscopic Evidence for the Formation of an N Intermediate during the Photocycle of Sensory Rhodopsin II (Phoborhodopsin) from <i>Natronobacterium Pharaonis</i> | |
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MedLine Citation:
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PMID: 21299224 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Sensory rhodopsin II is a seven transmembrane helical retinal protein and functions as a photoreceptor protein in negative phototaxis of halophilic archaea. Sensory rhodopsin II from Natronomonas pharaonis (NpSRII) is stable under various conditions and can be expressed functionally in Escherichia coli cell membranes. Rhodopsins from microorganisms, known as microbial rhodopsins, exhibit a photocycle, and light irradiation of these molecules leads to a high-energy intermediate, which relaxes thermally to the original pigment after passing through several intermediates. For bacteriorhodopsin (BR), a light-driven proton pump, the photocycle is established as BR → K → L → M → N → O → BR. The photocycle of NpSRII is similar to that of BR except for N, i.e., M thermally decays into the O, and N has not been well characterized in the photocycle. Thus we here examined the second half of the photocycle in NpSRII, and in the present transient absorption study we found the formation of a new photointermediate whose absorption maximum is ca. 500 nm. This intermediate becomes pronounced in the presence of azide, which accelerates the decay of M. Transient resonance Raman spectroscopy was further applied to demonstrate that this intermediate contains a 13-cis retinal protonated Schiff base. However, detailed analysis of the transient absorption data indicated that M-decay does not directly produce N, but rather produces O that is in equilibrium with N. This implies that N is not located in the main pathway of the intermediate sequence in the photocycle. These observations allowed us to propose a structural model for a photocycle that involves N. |
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Authors:
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Yusuke Tateishi; Takayuki Abe; Jun Tamogami; Yutaka Nakao; Takashi Kikukawa; Naoki Kamo; Masashi Unno |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-2-7 |
Journal Detail:
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Title: Biochemistry Volume: - ISSN: 1520-4995 ISO Abbreviation: - Publication Date: 2011 Feb |
Date Detail:
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Created Date: 2011-2-8 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0370623 Medline TA: Biochemistry Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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