Figure 1.

(A) An overall view of the crystal structure of Na⁺/K⁺-ATPase in its closed conformation (PDB code: 4HQJ). The protein is composed of three separate chains denoted as α-subunit (gray transmembrane region, dark gray A-domain, color scale P-domain as well as N-domain), β-subunit (light blue) and FYXD protein (light purple). The C45 loop of the α-subunit is composed of N- and P-domain. (B) A close-up view of the C45 loop structure with the cysteine residues (magenta) mutated in this study. (C) Simplified scheme of reactions forming the NKA catalytic cycle, sign “P” denotes the transiently autophosphorylated state of the enzyme.