Nunomura W, Takakuwa Y, Parra M, Conboy J, Mohandas N
Department of Biochemistry, School of Medicine, Tokyo Women's Medical University, Shinjuku, Tokyo 162-8666, Japan.
J Biol Chem. 2000 Aug 11;275(32):24540-6. doi: 10.1074/jbc.M002492200.
Three binary protein-protein interactions, glycophorin C (GPC)-4.1R, GPC-p55, and p55-4.1R, constitute the GPC-4.1R-p55 ternary complex in the erythrocyte membrane. Little is known regarding the molecular basis for the interaction of 4.1R with either GPC or p55 and regarding the role of 4.1R in regulating the various protein-protein interactions that constitute the GPC-4.1R-p55 ternary complex. In the present study, we present evidence that sequences in the 30-kDa domain encoded by exon 8 and exon 10 of 4.1R constitute the binding interfaces for GPC and p55, respectively. We further show that 4.1R increases the affinity of p55 binding to GPC by an order of magnitude, implying that 4.1R modulates the interaction between p55 and GPC. Finally, we document that binding of calmodulin to 4.1R decreases the affinity of 4.1R interactions with both p55 and GPC in a Ca(2+)-dependent manner, implying that the GPC-4.1R-p55 ternary protein complex can undergo dynamic regulation in the erythrocyte membrane. Taken together, these findings have enabled us to identify an important role for 4.1R in regulating the GPC-4.1R-p55 ternary complex in the erythrocyte membrane.
三种二元蛋白质-蛋白质相互作用，即血型糖蛋白C（GPC）-4.1R、GPC-p55和p55-4.1R，在红细胞膜中构成了GPC-4.1R-p55三元复合物。关于4.1R与GPC或p55相互作用的分子基础以及4.1R在调节构成GPC-4.1R-p55三元复合物的各种蛋白质-蛋白质相互作用中的作用，目前所知甚少。在本研究中，我们提供证据表明，由4.1R的外显子8和外显子10编码的30 kDa结构域中的序列分别构成了与GPC和p55的结合界面。我们进一步表明，4.1R使p55与GPC结合的亲和力提高了一个数量级，这意味着4.1R调节了p55与GPC之间的相互作用。最后，我们证明钙调蛋白与4.1R的结合以Ca(2+)依赖的方式降低了4.1R与p55和GPC相互作用的亲和力，这意味着GPC-4.1R-p55三元蛋白质复合物在红细胞膜中可经历动态调节。综上所述，这些发现使我们能够确定4.1R在调节红细胞膜中GPC-4.1R-p55三元复合物方面的重要作用。
