Doonan B
Med Hypotheses. 1985 Mar;16(3):265-77. doi: 10.1016/0306-9877(85)90009-x.
A model of anion and monovalent cation transport through a lipophilic water channel of the Na,K ATPase complex is presented. Literature data for the Na,K ATPase cation binding sites are combined with data for the anion binding sites of Band 3 to obtain adjacent cation and anion combining sites at the inner and outer channel mouths. Cations and anions form neutral ion pairs or undissociated acids at these sites and then partition much more favorably into lipophilic channel water, passing through the channel in diffusive fashion. Cation movements in an "uphill" direction occur without an enzyme translocating moiety and its specific energetic requirement. The pertinent factors are the exclusion of unpaired cations by the tight channel and the site selectivity or pickup ratios for Na/K at each side which dominate over bulk and transmembrane concentration ratios. ATP hydrolysis provides phosphate for ion pairing.
提出了一种通过钠钾ATP酶复合物的亲脂性水通道进行阴离子和单价阳离子转运的模型。钠钾ATP酶阳离子结合位点的文献数据与带3阴离子结合位点的数据相结合，以在通道内外口获得相邻的阳离子和阴离子结合位点。阳离子和阴离子在这些位点形成中性离子对或未解离的酸，然后更有利地分配到亲脂性通道水中，以扩散方式穿过通道。阳离子以“上坡”方向移动，无需酶转运部分及其特定的能量需求。相关因素包括紧密通道对未配对阳离子的排斥以及每一侧钠/钾的位点选择性或摄取率，这些因素比总体和跨膜浓度比更具主导性。ATP水解为离子配对提供磷酸根。
