Pavlov Evgeny, Grimbly Chelsey, Diao Catherine T M, French Robert J
Hotchkiss Brain Institute, Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alta., Canada T2N 4N1.
FEBS Lett. 2005 Sep 26;579(23):5187-92. doi: 10.1016/j.febslet.2005.08.032.
Reconstitution into planar lipid bilayers of a poly-3-hydroxybutyrate/calcium/polyphosphate (PHB/Ca(2+)/polyP) complex from Escherichia coli membranes yields cationic-selective, 100 pS channels (Das, S., Lengweiler, U.D., Seebach, D. and Reusch, R.N. (1997) Proof for a non-proteinaceous calcium-selective channel in Escherichia coli by total synthesis from (R)-3-hydroxybutanoic acid and inorganic polyphosphate. Proc. Natl. Acad. Sci. USA 94, 9075-9079). Here, we report that this complex can also form larger, weakly selective pores, with a maximal conductance ranging from 250pS to 1nS in different experiments (symmetric 150mM KCl). Single channels were inhibited by lanthanum (IC(50)=42+/-4microM, means+/-S.E.M.) with an unusually high Hill coefficient (8.4+/-1.2). Transition to low-conductance states (<250pS) was favored by increased membrane polarization (/V/ >or=50mV). High conductance states (>250pS) may reflect conformations important for genetic transformability, or "competence", of the bacterial cells, which requires the presence of the PHB/Ca(2+)/polyP complex in the membrane.
将来自大肠杆菌膜的聚-3-羟基丁酸酯/钙/多聚磷酸盐（PHB/Ca(2+)/多聚P）复合物重构成平面脂质双层，会产生阳离子选择性的100 pS通道（达斯，S.，伦格维勒，U.D.，泽巴赫，D.和罗伊施，R.N.（1997年）通过由（R）-3-羟基丁酸和无机多聚磷酸盐全合成，证明大肠杆菌中存在一种非蛋白质的钙选择性通道。美国国家科学院院刊94，9075 - 9079）。在此，我们报告该复合物还能形成更大的、选择性较弱的孔，在不同实验中（对称150mM KCl）最大电导范围为250pS至1nS。单通道受到镧的抑制（IC(50)=42±4μM，平均值±标准误），且具有异常高的希尔系数（8.4±1.2）。膜极化增加（/V/≥50mV）有利于向低电导状态（<250pS）转变。高电导状态（>250pS）可能反映了对细菌细胞的遗传转化能力或“感受态”很重要的构象，而这需要膜中存在PHB/Ca(2+)/多聚P复合物。
