A Model for the Homotypic Interaction between Na + ,K + -ATPase β 1 Subunits Reveals the Role of Extracellular Residues 221-229 in Its Ig-Like Domain

• Published in: International journal of molecular sciences 2019-09, Vol.20 (18)
• Main Authors: Páez, Omar, Martínez-Archundia, Marlet, Villegas-Sepúlveda, Nicolás, Roldan, María Luisa, Correa-Basurto, José, Shoshani, Liora
• Format: Article
• Language: English
• Subjects: Amino Acid Motifs; Animals; CHO Cells; Cricetulus; Models, Molecular; Molecular Docking Simulation; Molecular Dynamics Simulation; Mutagenesis, Site-Directed; Protein Binding; Protein Conformation; Sodium-Potassium-Exchanging ATPase - chemistry; Sodium-Potassium-Exchanging ATPase - genetics; Sodium-Potassium-Exchanging ATPase - metabolism
• ISSN: 1422-0067
• DOI: 10.3390/ijms20184538

The Na , K -ATPase transports Na and K across the membrane of all animal cells. In addition to its ion transporting function, the Na , K -ATPase acts as a homotypic epithelial cell adhesion molecule via its β subunit. The extracellular region of the Na , K -ATPase β subunit includes a single globular immunoglobulin-like domain. We performed Molecular Dynamics simulations of the ectodomain of the β subunit and a refined protein-protein docking prediction. Our results show that the β subunit Ig-like domain maintains an independent structure and dimerizes in an antiparallel fashion. Analysis of the putative interface identified segment Lys221-Tyr229. We generated triple mutations on YFP-β subunit fusion proteins to assess the contribution of these residues. CHO fibroblasts transfected with mutant β subunits showed a significantly decreased cell-cell adhesion. Association of β subunits in vitro was also reduced, as determined by pull-down assays. Altogether, we conclude that two Na , K -ATPase molecules recognize each other by a large interface spanning residues 221-229 and 198-207 on their β subunits.