Structure and Inhibition of the SARS Coronavirus Envelope Protein Ion Channel |
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Authors: | Konstantin Pervushin Edward Tan Krupakar Parthasarathy Xin Lin Feng Li Jiang Dejie Yu Ardcharaporn Vararattanavech Tuck Wah Soong Ding Xiang Liu Jaume Torres |
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Institution: | 1. School of Biological Sciences, Nanyang Technological University, Singapore.; 2. Biozentrum of University Basel, Basel, Switzerland.; 3. Center for Life Sciences, Department of Physiology, National University of Singapore, Singapore.; 4. Institute of Molecular Cell Biology, Proteos, Singapore.;University of North Carolina, United States of America |
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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. |
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