Substitution of transmembrane residues with hydrogen-bonding potential in the alpha subunit of Na,K-ATPase reveals alterations in ouabain sensitivity

The effect of hydrogen-bonding (H-bonding) amino acids on the ouabain affinity of sodium- and potassium-activated adenosinetriphosphatase (Na,K-ATPase) was investigated. The study protocol involved site-directed mutagenesis to substitute the transmembrane residues with hydrogen-binding potential in the NA,K-ATPase alpha subunit with residues that cannot participate in H-bonding. The results showed that tyrosine-108 and cysteine-104 are major determinants of Na,K-ATPase affinity for ouabain.