Barwe Sonali P, Kim Sanguk, Rajasekaran Sigrid A, Bowie James U, Rajasekaran Ayyappan K
Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095, USA.
J Mol Biol. 2007 Jan 19;365(3):706-14. doi: 10.1016/j.jmb.2006.10.029. Epub 2006 Oct 31.
Na,K-ATPase is a hetero-oligomer of alpha and beta-subunits. The Na,K-ATPase beta-subunit (Na,K-beta) is involved in both the regulation of ion transport activity, and in cell-cell adhesion. By structure prediction and evolutionary analysis, we identified two distinct faces on the Na,K-beta transmembrane domain (TMD) that could mediate protein-protein interactions: a glycine zipper motif and a conserved heptad repeat. Here, we show that the heptad repeat face is involved in the hetero-oligomeric interaction of Na,K-beta with Na,K-alpha, and the glycine zipper face is involved in the homo-oligomerization of Na,K-beta. Point mutations in the heptad repeat motif reduced Na,K-beta binding to Na,K-alpha, and Na,K-ATPase activity. Na,K-beta TMD homo-oligomerized in biological membranes, and mutation of the glycine zipper motif affected oligomerization and cell-cell adhesion. These results provide a structural basis for understanding how Na,K-beta links ion transport and cell-cell adhesion.
钠钾-ATP酶是由α和β亚基组成的异源寡聚体。钠钾-ATP酶β亚基（Na,K-β）既参与离子转运活性的调节，也参与细胞间黏附。通过结构预测和进化分析，我们在Na,K-β跨膜结构域（TMD）上鉴定出两个不同的面，它们可能介导蛋白质-蛋白质相互作用：一个甘氨酸拉链基序和一个保守的七肽重复序列。在此，我们表明七肽重复序列面参与Na,K-β与Na,K-α的异源寡聚体相互作用，而甘氨酸拉链面参与Na,K-β的同源寡聚化。七肽重复基序中的点突变降低了Na,K-β与Na,K-α的结合以及钠钾-ATP酶活性。Na,K-β TMD在生物膜中进行同源寡聚化，甘氨酸拉链基序的突变影响寡聚化和细胞间黏附。这些结果为理解Na,K-β如何连接离子转运和细胞间黏附提供了结构基础。
