Le Dain A C, Saint N, Kloda A, Ghazi A, Martinac B
Department of Pharmacology, University of Western Australia, Nedlands, WA 6907, Australia.
J Biol Chem. 1998 May 15;273(20):12116-9. doi: 10.1074/jbc.273.20.12116.
Mechanosensitive (MS) ion channels have been documented in a variety of cells belonging to Eukarya and Eubacteria. We report the novel finding of two types of MS ion channels in the cell membrane of the halophilic archaeon Haloferax volcanii, a member of the Archaea that comprise the third phylogenetic domain. The two channels, MscA1 and MscA2, differed in their kinetic properties with MscA1 exhibiting more frequent open-closed transitions than MscA2. Both channels have large conductances that rectify between -40 mV and +40 mV where the conductance of MscA1 ranged from 380 to 680 picosiemens, whereas MscA2 ranged from 850 to 490 picosiemens. Both channels were blocked by submillimolar gadolinium. In addition, the channels of either membrane vesicles or detergent-solubilized membrane proteins remained functional upon reconstitution into artificial liposomes, a result that indicates that these channels are activated by mechanical force transmitted via the lipid bilayer alone. Subsequently a 37-kDa protein corresponding to the MscA1 channel activity was purified. With the possible functional similarity to bacterial MS channels, our finding of MS channels in Archaea emphasizes the ubiquity and importance of these channels in all domains of the evolutionary tree.
机械敏感（MS）离子通道已在属于真核生物和真细菌的多种细胞中被记录。我们报告了在嗜盐古菌沃氏嗜盐栖热菌细胞膜中发现的两种新型MS离子通道，沃氏嗜盐栖热菌是构成第三个系统发育域的古菌成员。这两种通道，即MscA1和MscA2，其动力学特性不同，MscA1比MscA2表现出更频繁的开闭转换。两种通道都具有大电导，在-40 mV至+40 mV之间整流，其中MscA1的电导范围为380至680皮西门子，而MscA2的电导范围为850至490皮西门子。两种通道都被亚毫摩尔浓度的钆阻断。此外，膜囊泡或去污剂增溶的膜蛋白中的通道在重构到人工脂质体中后仍保持功能，这一结果表明这些通道仅由通过脂质双层传递的机械力激活。随后纯化了一种与MscA1通道活性相对应的37 kDa蛋白。鉴于与细菌MS通道可能存在功能相似性，我们在古菌中发现MS通道强调了这些通道在进化树所有域中的普遍性和重要性。
