Conductance and amantadine binding of a pore formed by a lysine‐flanked transmembrane domain of SARS coronavirus envelope protein

Abstract

The coronavirus responsible for the severe acute respiratory syndrome (SARS-CoV) contains a small envelope protein, E, with putative involvement in host cell apoptosis and virus morphogenesis. It has been suggested that E protein can form a membrane destabilizing transmembrane (TM) hairpin, or homooligomerize to form a regular TM a-helical bundle. We have shown previously that the topology of the a-helical putative TM domain of E protein (ETM), flanked by two lysine residues at C and N termini to improve solubility, is consistent with a regular TM a-helix, with orientational parameters in lipid bilayers that are consistent with a homopentameric model. Herein, we show that this peptide, reconstituted in lipid bilayers, shows sodium conductance. Channel activity is inhibited by the antiinfluenza drug amantadine, which was found to bind our preparation with moderate affinity. Results obtained from single or double mutants indicate that the organization of the transmembrane pore is consistent with our previously reported pentameric a-helical bundle model.

The Coronavirus E Protein: Assembly and Beyond

“…This possibility was originally addressed using computational modeling, which predicted that the E protein HD could form stable dimers, trimers, and pentamers [62]. This prediction was further bolstered by several spectroscopic studies, which showed that the HD of SARS-CoV E forms a pentamer [63,64,65]. However, this result has not been confirmed for the other E proteins, or for the full length SARS-CoV E protein in a natural membrane.…”

MERS coronavirus envelope protein has a single transmembrane domain that forms pentameric ion channels

“…SARS-CoV E protein has been shown unequivocally to have just one TM domain , and is the only E protein for which structural data is available Pervushin et al, 2009). E proteins have been shown to form ion channels in synthetic membranes (Torres et al, 2007;Wilson et al, 2006), with reported conductance of 20-30 pS. However, characterization with properly purified full length and transmembrane peptides of SARS-CoV E protein has produced much higher (>10 times) conductances Verdia-Baguena et al, 2012, 2013a.…”

Viral proteins function as ion channels

“…In Coronaviridae, it was demonstrated that the envelope (E) proteins of MHV, SARS-CoV, HCoV-229E and IBV exhibit viroporin activity [35,37,38,[100][101][102][103]. The E protein of SARS-CoV is 76 amino acids long, contains one predicted TM domain and forms a pentameric ion channel [35,36,103,104]. The SARS-CoV E protein is more selective for Na + than for K + ions, status similar to that of Alphavirus 6 K proteins [11].…”