2010 Fiscal Year Final Research Report
A developmental approach to clarify a molecular mechanism of transporter utilizing a model transporter as a light-driven ion pump
| Project/Area Number |
20590031
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical pharmacy
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| Research Institution | Matsuyama University |
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Principal Investigator |
MIYAUCHI Seiji Matsuyama University, 薬学部, 教授 (30202352)
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| Co-Investigator(Kenkyū-buntansha) |
KIKUKAWA Takashi 北海道大学, 創成科学共同研究機構, 助教 (20281842)
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| Project Period (FY) |
2008 – 2010
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| Keywords | 生物物理化学 / トランスポーター / 光駆動性イオンポンプ / ハロロドプシン / 輸送分子機構 / スイッチ機構 / 分子弁 |
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| Research Abstract |
Halorhodopsin (HR) is a light-driven inward-directed Cl^- pump. To clarify the molecular mechanism of Cl^- transport in detail, we precisely determined the transport activities through HR with various physicochemical techniques, and the following results were obtained.
(1) The crystal structure clearly shows that the primary Cl^- is proximal to the protonated Schiff base (PSB) and is stabilized by electrostatic interactions with the positive charged PSB [PDB : 1E12]. Based on the crystal structure, we mutated amino acid residues, which might be involved in Cltransport. Several important amino acid residues were identified ; Arg123, Ser130 and Asp252.
(2) Especially, two amino acid residues Ser130 and Asp252 were proved out to play an important role in Cl^- translocation away from the binding site in the extracellular (EC) channel across the retinal.
(3) For the sake of the vectorial translocation, HR protein must possess one or several molecular valves in HR to hinder the Cl^- leakage, or backflow (from cytoplasmic (CP) to EC channel) during pumping cycles. Ser130 coordinates with PBS and functions as a molecular valve to hinder the internal leak, backflux of Cl^- during anion-transport cycle.
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