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.
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.
Coronaviruses (family Coronaviridae, genus Coronavirus) are enveloped viruses that cause common colds in humans and a variety of lethal diseases in birds and mammals –. The virus species in the genus Coronavirus have been organized into 3 groups, using genetic and antigenic criteria . 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) ,. Group 3 includes the avian Infectious bronchitis virus (IBV) and the turkey coronavirus (TCoV).