Evidence for the Formation of a Heptameric Ion Channel Complex by the Hepatitis C Virus P7 Protein in Vitro

Abstract

The p7 protein of hepatitis C virus functions as an ion channel both in vitro and in cell-based assays and is inhibited by amantadine, long alkyl chain imino-sugar derivatives, and amiloride compounds. Future drug design will be greatly aided by information on the stoichiometry and high resolution structure of p7 ion channel complexes. Here, we have refined a bacterial expression system for p7 based on a glutathione S-transferase fusion methodology that circumvents the inherent problems of hydrophobic protein purification and the limitations of chemical synthesis. Rotational averaging and harmonic analysis of transmission electron micrographs of glutathione S-transferase-FLAG-p7 fusion proteins in liposomes revealed a heptameric stoichiometry. The oligomerization of p7 protein was then confirmed by SDS-PAGE and mass spectrometry analysis of pure, concentrated FLAG-p7. The same protein was also confirmed to function as an ion channel in suspended lipid bilayers and was inhibited by amantadine. These data validate this system as a means of generating high resolution structural information on the p7 ion channel complex.