Na channel reconstruction

Orai1

イオンチャネルは、神経などの興奮細胞でのイオン流入の研究により発見された。しかし、非興奮細胞でも情報伝達に重要なイオンチャネルが存在する。特に、免疫機構に必須なOrai1はSOCであり、本研究ではその精製に成功し、さらにその構造を突き止めた。細胞質側に突起を持ち、小胞内Caイオンセンサー・STIMと直接結合すると思われる。

 

 

 


Abstract from: J Biol Chem. 2009 May 15;284(20):13676-85. Epub 2009 Mar 16.

 

Tetrameric Orai1 is a teardrop-shaped molecule with a long, tapered cytoplasmic domain.

Maruyama Y, Ogura T, Mio K, Kato K, Kaneko T, Kiyonaka S, Mori Y, Sato C.

Neuroscience Research Institute and Biological Information Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-4 Umezono, Tsukuba 305-8568, Japan.

The Ca(2+) release-activated Ca(2+) channel is a principal regulator of intracellular Ca(2+) rise, which conducts various biological functions, including immune responses. This channel, involved in store-operated Ca(2+) influx, is believed to be composed of at least two major components. Orai1 has a putative channel pore and locates in the plasma membrane, and STIM1 is a sensor for luminal Ca(2+) store depletion in the endoplasmic reticulum membrane. Here we have purified the FLAG-fused Orai1 protein, determined its tetrameric stoichiometry, and reconstructed its three-dimensional structure at 21-Å resolution from 3681 automatically selected particle images, taken with an electron microscope. This first structural depiction of a member of the Orai family shows an elongated teardrop-shape 150Å in height and 95Å in width. Antibody decoration and volume estimation from the amino acid sequence indicate that the widest transmembrane domain is located between the round extracellular domain and the tapered cytoplasmic domain. The cytoplasmic length of 100Å is sufficient for direct association with STIM1. Orifices close to the extracellular and intracellular membrane surfaces of Orai1 seem to connect outside the molecule to large internal cavities.

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タンパク質構造決定技術、膜タンパク質精製技術、情報技術、電子顕微鏡技術、神経細胞の培養技術等.