Shiffer K A, Goodman S R
Proc Natl Acad Sci U S A. 1984 Jul;81(14):4404-8. doi: 10.1073/pnas.81.14.4404.
125I-labeled protein 4.1a and 4.1b have equal ability to reassociate with inside-out erythrocyte vesicles that were depleted of protein 4.1 in addition to other peripheral membrane proteins. The reassociation of 125I-labeled protein 4.1 to protein 4.1-depleted vesicles at 4 degrees C is salt dependent, pH dependent, and saturable with a Kd of 42-50 nM and an extrapolated maximal binding capacity of 120-140 micrograms of protein 4.1 bound per mg of vesicle protein or 60-70 micrograms of protein 4.1 bound per mg of ghost protein, correlating with the protein 4.1 content in the erythrocyte membrane (6-7% of the total membrane protein). Selective proteolytic cleavage of these vesicles with papain (5 micrograms/ml at 4 degrees C) eliminates greater than 60% of the high-affinity binding sites; therefore, we conclude that the interaction of protein 4.1 with the cytoplasmic membrane surface is through a specific high-affinity protein-protein association.
125I标记的蛋白4.1a和4.1b与内翻式红细胞囊泡重新结合的能力相同，这些囊泡除了其他外周膜蛋白外，还缺乏蛋白4.1。在4℃下，125I标记的蛋白4.1与缺乏蛋白4.1的囊泡的重新结合是盐依赖性、pH依赖性的，并且具有饱和性，解离常数（Kd）为42 - 50 nM，外推的最大结合能力为每毫克囊泡蛋白结合120 - 140微克蛋白4.1，或每毫克空泡蛋白结合60 - 70微克蛋白4.1，这与红细胞膜中蛋白4.1的含量（占总膜蛋白的6 - 7%）相关。用木瓜蛋白酶（4℃下5微克/毫升）对这些囊泡进行选择性蛋白水解切割，可消除超过60%的高亲和力结合位点；因此，我们得出结论，蛋白4.1与细胞质膜表面的相互作用是通过特定的高亲和力蛋白 - 蛋白结合实现的。
