Molecular mechanisms of water and solute transport across archaebacterial lipid membranes
Molecular mechanisms of water and solute transport across archaebacterial lipid membranes
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DOI：
10.1074/jbc.m103265200
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发表时间：
2001-07-20
影响因子：
4.8
通讯作者：
Zeidel, ML
中科院分区：
文献类型：
--
作者：
Mathai, JC;Sprott, GD;Zeidel, ML
古生菌在无生物、饱和盐分和高、低极端温度和pH的环境中茁壮成长，它们的大部分膜脂是极性的，其特征是古生代的结构特征，其典型特征是甘油骨架与定长的异戊二烯链的乙醚连接，通常是完全饱和的，并且具有与细菌和真核生物的甘油脂相反的sn-2，3立体化学。这些细菌还特有的大环古生酚和跨越钙质脂类的膜存在于一些极端的嗜热菌和产甲烷菌中，为了确定古生菌膜的屏障功能并检验这些独特的结构特征对渗透能力的影响，我们研究了水、甘油(和尿素)、质子、以及由这些脂类形成的脂质体的氨气渗透性。与二植酸磷脂酰胆碱脂质体相比，大环考古醇和钙铁醇脂类均显著降低脂质体的水、氨、尿素和甘油的渗透率(6-120倍)，醚键和植酸链的存在对这些渗透率没有显著影响，而表观质子渗透率因乙醚键的存在而降低了S倍。大环考古醇和钙质醇结构的存在使膜的表观质子渗透率进一步降低了10-17倍，这些结果表明，大环考古酚和钙质醇脂类形成的膜的中面碳氢区的极限迁移率在降低脂膜的通透性方面起着重要作用。此外，用乙醚取代酯键似乎为质子流动提供了一个额外的障碍。
Archaebacteria thrive in environments characterized by anaeobiosis, saturated salt, and both high and low extremes of temperature and pH, The bulk of their membrane lipids are polar, characterized by the archaeal structural features typified by ether linkage of the glycerol backbone to isoprenoid chains of constant length, often fully saturated, and with sn-2,3 stereochemistry opposite that of glycerolipids of Bacteria and Eukarya, Also unique to these bacteria are macrocyclic archaeol and membrane spanning caldarchaeol lipids that are found in some extreme thermophiles and methanogens, To define the barrier function of archaebacterial membranes and to examine the effects of these unique structural features on permeabilities, we investigated the water, solute (urea and glycerol), proton, and ammonia permeability of liposomes formed by these lipids. Both the macrocyclic archaeol and caldarchaeol lipids reduced the water, ammonia, urea, and glycerol permeability of Liposomes significantly (6-120-fold) compared with diphytanylphosphatidylcholine liposomes, The presence of the ether bond and phytanyl chains did not significantly affect these permeabilities, However, the apparent proton permeability was reduced S-fold by the presence of an ether bond. The presence of macrocyclic archaeol and caldarchaeol structures further reduced apparent proton permeabilities by 10-17-fold, These results indicate that, the limiting mobility of the midplane hydrocarbon region of the membranes formed by macrocyclic archaeol and caldarchaeol lipids play a significant role in reducing the permeability properties of the lipid membrane. In addition, it appears that substituting ether for ester bonds presents an additional barrier to proton flux.