Gu Li-Qun, Cheley Stephen, Bayley Hagan
Department of Medical Biochemistry and Genetics, Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA.
Proc Natl Acad Sci U S A. 2003 Dec 23;100(26):15498-503. doi: 10.1073/pnas.2531778100. Epub 2003 Dec 15.
The flux of solvent water coupled to the transit of ions through protein pores is considerable. The effect of this electroosmotic solvent flow on the binding of a neutral molecule [beta-cyclodextrin (betaCD)] to sites within the staphylococcal alpha-hemolysin pore was investigated. Mutant alpha-hemolysin pores were used to which betaCD can bind from either entrance and through which the direction of water flow can be controlled by choosing the charge selectivity of the pore and the polarity of the applied potential. The Kd values for betaCD for individual mutant pores varied by >100-fold with the applied potential over a range of -120 to +120 mV. In all cases, the signs of the changes in binding free energy and the influence of potential on the association and dissociation rate constants for betaCD were consistent with an electroosmotic effect.
与离子通过蛋白质孔道转运相耦合的溶剂水分子通量相当可观。研究了这种电渗溶剂流对中性分子[β-环糊精(βCD)]与葡萄球菌α-溶血素孔道内位点结合的影响。使用了突变型α-溶血素孔道,βCD可以从任一入口与之结合,并且通过选择孔道的电荷选择性和所施加电势的极性,可以控制水流的方向。在-120至+120 mV范围内,随着所施加电势的变化,各个突变型孔道的βCD的解离常数(Kd)值变化超过100倍。在所有情况下,结合自由能变化的符号以及电势对βCD缔合和解离速率常数的影响均与电渗效应一致。