title: Analysis of SARS-CoV E protein ion channel activity by tuning the protein and lipid charge.
abstract: A partial characterization of the ion channels formed by the SARS coronavirus (CoV) envelope (E) protein was previously reported (C. Verdiá-Báguena et al., 2012 [12]). Here, we provide new significant insights on the involvement of lipids in the structure and function of the CoV E protein channel on the basis of three series of experiments. First, reversal potential measurements over a wide range of pH allow the dissection of the contributions to channel selectivity coming from ionizable residues of the protein transmembrane domain and also from the negatively charged groups of diphytanoyl phosphatidylserine (DPhPS) lipid. The corresponding effective pKas are consistent with the model pKas of the acidic residue candidates for titration. Second, the change of channel conductance with salt concentration reveals two distinct regimes (Donnan-controlled electrodiffusion and bulk-like electrodiffusion) fully compatible with the outcomes of selectivity experiments. Third, by measuring channel conductance in mixtures of neutral diphytanoyl phosphatidylcholine (DPhPC) lipids and negatively charged DPhPS lipids in low and high salt concentrations we conclude that the protein-lipid conformation in the channel is likely the same in charged and neutral lipids. Overall, the whole set of experiments supports the proteolipidic structure of SARS-CoV E channels and explains the large difference in channel conductance observed between neutral and charged membranes.
authors.affiliation: Department of Physics, Laboratory of Molecular Biophysics, Universitat Jaume I, 12071 Castellón, Spain.
authors.forename: Carmina
authors.initials: C
authors.lastname: Verdiá-Báguena
authors.forename: Jose L
authors.initials: JL
authors.lastname: Nieto-Torres
authors.forename: Antonio
authors.initials: A
authors.lastname: Alcaraz
authors.forename: Marta L
authors.initials: ML
authors.lastname: Dediego
authors.forename: Luis
authors.initials: L
authors.lastname: Enjuanes
authors.forename: Vicente M
authors.initials: VM
authors.lastname: Aguilella
mesh_terms: D000595:Amino Acid Sequence; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000737:chemistry*; D017136:Ion Transport; D008051:Lipid Bilayers / Q000737:chemistry*; D008564:Membrane Potentials; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry; D011188:Potassium / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D045473:Severe acute respiratory syndrome-related coronavirus / Q000737:chemistry*; D055672:Static Electricity; D014759:Viral Envelope Proteins / Q000737:chemistry*; D000086082:Viroporin Proteins
chemical_list: C501689:E protein, SARS coronavirus; D007473:Ion Channels; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D014759:Viral Envelope Proteins; D000086082:Viroporin Proteins; C021016:1,2-diphytanoylphosphatidylcholine; D011188:Potassium
keywords: Coronavirus; Envelope protein; Ion channel; Lipid charge; SARS