Isolation and purification of the extracellular and intracellular portions of the beta subunit of (Na+,K+)-ATPase.

The beta subunit of lamb kidney (Na+,K+)-ATPase was isolated by size exclusion high performance liquid chromatography. Treatment of the beta subunit with formic acid yielded two peptide fragments which were purified via reversed phase high performance liquid chromatography. These peptides were identified by sodium dodecylsulfate polyacrylamide gel electrophoresis, amino acid analysis and N-terminal sequencing as (Pro 94-Ser 302), a largely hydrophilic peptide which comprises the major portion of the extracellular domain including six Cys residues which participate in disulfide bond formation and three glycosylation sites and a smaller peptide (Ala 1-Asp 93) which contains the single membrane spanning region and the intracellular domain.