Research Article: Structure and Inhibition of the SARS Coronavirus Envelope Protein Ion Channel

Date Published: July 10, 2009

Publisher: Public Library of Science

Author(s): Konstantin Pervushin, Edward Tan, Krupakar Parthasarathy, Xin Lin, Feng Li Jiang, Dejie Yu, Ardcharaporn Vararattanavech, Tuck Wah Soong, Ding Xiang Liu, Jaume Torres, Ralph S. Baric.

http://doi.org/10.1371/journal.ppat.1000511

Abstract

The envelope (E) protein from coronaviruses is a small polypeptide that contains at least one α-helical transmembrane domain. Absence, or inactivation, of E protein results in attenuated viruses, due to alterations in either virion morphology or tropism. Apart from its morphogenetic properties, protein E has been reported to have membrane permeabilizing activity. Further, the drug hexamethylene amiloride (HMA), but not amiloride, inhibited in vitro ion channel activity of some synthetic coronavirus E proteins, and also viral replication. We have previously shown for the coronavirus species responsible for severe acute respiratory syndrome (SARS-CoV) that the transmembrane domain of E protein (ETM) forms pentameric α-helical bundles that are likely responsible for the observed channel activity. Herein, using solution NMR in dodecylphosphatidylcholine micelles and energy minimization, we have obtained a model of this channel which features regular α-helices that form a pentameric left-handed parallel bundle. The drug HMA was found to bind inside the lumen of the channel, at both the C-terminal and the N-terminal openings, and, in contrast to amiloride, induced additional chemical shifts in ETM. Full length SARS-CoV E displayed channel activity when transiently expressed in human embryonic kidney 293 (HEK-293) cells in a whole-cell patch clamp set-up. This activity was significantly reduced by hexamethylene amiloride (HMA), but not by amiloride. The channel structure presented herein provides a possible rationale for inhibition, and a platform for future structure-based drug design of this potential pharmacological target.

Partial Text

Coronaviruses (family Coronaviridae, genus Coronavirus[1]) are enveloped viruses that cause common colds in humans and a variety of lethal diseases in birds and mammals [2]–[4]. The virus species in the genus Coronavirus have been organized into 3 groups, using genetic and antigenic criteria [5]. Group 1 is subdivided into two groups, 1a and 1b. Group 1a includes the porcine Transmissible gastroenteritis virus (TGEV), whereas group 1b includes Human coronaviruses 229E (HCoV-229E) or NL63 (HCoV-NL63). Group 2 is also subdivided in groups 2a, e.g., Murine hepatitis virus (MHV) and Human coronavirus OC43 (HCoV-OC43) and 2b, e.g., the virus responsible for the severe acute respiratory syndrome (SARS-CoV) [6],[7]. Group 3 includes the avian Infectious bronchitis virus (IBV) and the turkey coronavirus (TCoV).

 

Source:

http://doi.org/10.1371/journal.ppat.1000511