Ion channels formed by NB, an influenza B virus protein

The influenza B virus protein, NE, was expressed in Escherichia coli, either with a C-terminal polyhistidine tag or with NE fused to the C-terminus of glutathione S-transferase (GST), and purified by affinity chromatography. NE produced ion channel activity when added to artificial lipid bilayers separating NaCl solutions with unequal concentrations (150-500 mM cis, 50 mM trans). An antibody to a peptide mimicking the 25 residues at the C-terminal end of NE, and amantadine at high concentration (2-3 mM), both depressed ion channel activity. Ion channels had a variable conductance, the lowest conductance observed being approximately 10 picosiemens. At a pH of 5.5 to 6.5, currents reversed at positive potentials indicating that the channel was more permeable to sodium than to chloride ions (P-Na/P-Cl similar to 9). In asymmetrical NaCl solutions at a pH of 2.5, currents reversed closer to the chloride than to the sodium equilibrium potential indicating that the channel had become more permeable to chloride than to sodium ions (P-Cl/P-Na similar to 4). It was concluded that, at normal pHs, NE forms cation-selective channels.