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-t erminus of glutathione S-transferase (GST), and purified by affinity c hromatography. NE produced ion channel activity when added to artifici al lipid bilayers separating NaCl solutions with unequal concentration s (150-500 mM cis, 50 mM trans). An antibody to a peptide mimicking th e 25 residues at the C-terminal end of NE, and amantadine at high conc entration (2-3 mM), both depressed ion channel activity. Ion channels had a variable conductance, the lowest conductance observed being appr oximately 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 chlori de than to the sodium equilibrium potential indicating that the channe l 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.