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

ABSTRACT: 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 ?1 subunit. The extracellular region of the Na+, K+-ATPase ?1 subunit includes a single globular immunoglobulin-like domain. We performed Molecular Dynamics simulations of the ectodomain of the ?1 subunit and a refined protein-protein docking prediction. Our results show that the ?1 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-?1 subunit fusion proteins to assess the contribution of these residues. CHO fibroblasts transfected with mutant ?1 subunits showed a significantly decreased cell-cell adhesion. Association of ?1 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 ?1 subunits.

SUBMITTER: Paez O 

PROVIDER: S-EPMC6770782 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature