Structure and Inhibition of the SARS Coronavirus Envelope Protein Ion Channel

Pervushin, Konstantin; Tan, Edward; Parthasarathy, Krupakar; Lin, Xin; Jiang, Feng Li; Yu, Dejie; Vararattanavech, Ardcharaporn; Soong, Tuck Wah; Liu, Ding Xiang; Torres, Jaume

The ETM pentameric channel ETM shows a sufficiently resolved 1 H NMR spectra. However, to facilitate resonance assignment and to unequivocally identify inter-monomer NOEs, six labeled amino acids were chemically incorporated near the center of the ETM a-helix. Selection of appropriate specific labels is facilitated by prediction of likely intermonomer interactions using other lower resolution biophysical techniques. In particular, the model reconstructed here with NMR data is consistent with a model that was derived from the analysis of evolutionary conservation of ETM in coronavirus envelope proteins [40] . The latter approach is data independent, and only relies on the reasonable assumption that all homologues share the same backbone structure [42] . Because by definition conservative mutations that appear during evolution should not destabilize the correct model of transmembrane interaction, but may destabilize incorrect low energy models that appear during the simulations along with the correct model, these mutations act effectively as an in silico filter [43] . The inter-helical orientation obtained for the ETM a-helices, and their orientation respect to the lumen of the ETM channel and detergent phase, is also in agreement with previous ETM helix rotational orientation measurements obtained by infrared linear dichroism [38] .