title: Structure and ion channel activity of the human respiratory syncytial virus (hRSV) small hydrophobic protein transmembrane domain.
abstract: The small hydrophobic (SH) protein from the human respiratory syncytial virus (hRSV) is a glycoprotein of approximately 64 amino acids with one putative alpha-helical transmembrane domain. Although SH protein is important for viral infectivity, its exact role during viral infection is not clear. Herein, we have studied the secondary structure, orientation, and oligomerization of the transmembrane domain of SH (SH-TM) in the presence of lipid bilayers. Only one oligomer, a pentamer, was observed in PFO-PAGE. Using polarized attenuated total reflection-Fourier transform infrared (PATR-FTIR) spectroscopy, we show that the SH-TM is alpha-helical. The rotational orientation of SH-TM was determined by site-specific infrared dichroism (SSID) at two consecutive isotopically labeled residues. This orientation is consistent with that of an evolutionary conserved pentameric model obtained from a global search protocol using 13 homologous sequences of RSV. Conductance studies of SH-TM indicate ion channel activity, which is cation selective, and inactive below the predicted pK(a) of histidine. Thus, our results provide experimental evidence that the transmembrane domain of SH protein forms pentameric alpha-helical bundles that form cation-selective ion channels in planar lipid bilayers. We provide a model for this pore, which should be useful in mutagenesis studies to elucidate its role during the virus cycle.
authors: School of Biological Sciences, Nanyang Technological University, 637551 Singapore.
authors: Siok Wan
authors: SW
authors: Gan
authors: Lifang
authors: L
authors: Ng
authors: Xin
authors: X
authors: Lin
authors: Xiandi
authors: X
authors: Gong
authors: Jaume
authors: J
authors: Torres
mesh_terms: D000595:Amino Acid Sequence; D002412:Cations / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D006860:Hydrogen Bonding; D007473:Ion Channels / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D018113:Respiratory Syncytial Virus, Human / Q000378:metabolism*; D015682:Retroviridae Proteins, Oncogenic / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002412:Cations; D007473:Ion Channels; D008051:Lipid Bilayers; D015682:Retroviridae Proteins, Oncogenic; C056150:small hydrophobic protein, virus