Rae J L, Shepard A R
Department of Physiology, May Foundation, Rochester, MN 55905, USA.
Exp Eye Res. 1998 Mar;66(3):347-59. doi: 10.1006/exer.1997.0432.
Lens epithelial cells from many species contain inwardly rectifying K+ channels. The channels are highly selective for K+ over Na+. They have a conductance of 27-30 pS in symmetrical 150 mM K+ solutions. The conductance to inwardly flowing current depends on the external [K+], being 1/2 maximal at about 50 mM and maximal by 110-150 mM. The amino acid sequences from lens epithelium (eight different species) show at least 98% sequence homology to each other and to the potassium channel known as IRK1 (Kir 2.1). Cloned channels from chick, rabbit, and human lens epithelium all make functional channels when their cDNA is transfected into HEK-293 or tsA-201 cells. Human lens inward rectifiers when engineered as fusion proteins with green fluorescent protein (GFP) also make functional channels. In addition, their localization in the membrane and in intracellular organelles can be demonstrated by fluorescence microscopy.
许多物种的晶状体上皮细胞都含有内向整流钾通道。这些通道对钾离子的选择性远高于钠离子。在对称的150 mM钾离子溶液中，它们的电导为27 - 30 pS。内向电流的电导取决于外部[钾离子]浓度，在约50 mM时为最大值的1/2，在110 - 150 mM时达到最大值。来自晶状体上皮（八个不同物种）的氨基酸序列彼此之间以及与称为IRK1（Kir 2.1）的钾通道显示出至少98%的序列同源性。当将来自鸡、兔和人类晶状体上皮的克隆通道的cDNA转染到HEK - 293或tsA - 201细胞中时，它们都能形成功能性通道。当将人类晶状体内向整流器构建为与绿色荧光蛋白（GFP）的融合蛋白时，也能形成功能性通道。此外，通过荧光显微镜可以证明它们在膜和细胞内细胞器中的定位。
