Ionophore properties of peptide fragments of brain Na+,K+-Atpase

Polypeptide fragments from Na+, K+-ATPase of cattle brain are obtained by the bromocyan-treatment of the protein and subsequent gel filtration via sephadexes; the fragments were reconstructed into bilayer lipid membranes (BLM). Polypeptides of fractions I and II induce cationic and polypeptides of fraction IV--cationic-anionic conductivity of BLM. Neither sodium nor potassium selectivity of BLM modified by protein fragments of fractions I and II was observed. Fluctuations of the modified membranes current are of spasmodic character, ATP and inhibitors of the sodium pump do not affect them. The induction of current fluctuations peculiar to channels into BLM is supposed to be a character of polypeptides obtained after the ATPase splitting but not of the cation-transport system of the sodium pump.