title: An amino-acid substitution in the influenza-B NB protein affects ion-channel gating.
abstract: The effects of site-directed mutations in NB, a protein encoded by the influenza B virus that has been shown to form cation-selective ion channels at pH 6.0, were studied on ion channel characteristics in artificial lipid bilayers. It was thought that the residues in the hydrophobic region of NB we selected for mutation might be involved in the transport of cations across the channel and that changes in these residues might affect channel properties such as gating and ion-selectivity. Serine residues at positions 20 and 28, threonine at position 24 and cysteine at position 26 were replaced by alanine. We found that the mutation S20A gave channels that did not gate and that remained open most of the time. Proton permeability of NB channels, as detected by fluorescence quenching, was also altered by the mutation S20A: channels were no longer proton-permeable. The other mutations, S28A, T24A and C26A, did not have any detectable effect on the activity or proton permeability of channels formed by NB. The results indicate that serine 20 may have an important role in normal function of NB channels.
authors.affiliation: Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, P.O. Box 334, Canberra City, ACT 2601, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Premkumar
authors.forename: G D
authors.initials: GD
authors.lastname: Ewart
authors.forename: G B
authors.initials: GB
authors.lastname: Cox
authors.forename: P W
authors.initials: PW
authors.lastname: Gage
mesh_terms: D019943:Amino Acid Substitution; D015640:Ion Channel Gating; D007473:Ion Channels; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D008564:Membrane Potentials; D008567:Membranes, Artificial; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000737:chemistry*
chemical_list: D007473:Ion Channels; D008051:Lipid Bilayers; D008567:Membranes, Artificial; C051094:NB glycoprotein, Influenza B virus; D011994:Recombinant Proteins; D014764:Viral Proteins