The extracellular domain of immunodeficiency virus gp41 protein: Expression in Escherichia coli, purification, and crystallization

Abstract

The env gene of SIV and HIV‐1 encodes a single glycoprotein gp160, which is processed to give a noncovalent complex of the soluble glycoprotein gp120 and the transmembrane glycoprotein gp41. The extracellular region (ectodomain), minus the N‐terminal fusion peptide, of gp41 from HIV‐1 (residues 27‐154) and SIV (residues 27‐149) have been expressed in Escherichia coli. These insoluble proteins were solubilized and subjected to a simple purification and folding scheme, which results in high yields of soluble protein. Purified proteins have a trimeric subunit composition and high a‐helical content, consistent with the predicted coil‐coil structure. SIV gp41 containing a double cysteine mutation was crystallized. The crystals are suitable for X‐ray structure determination and, preliminary analysis, together with additional biochemical evidence, indicates that the gp41 trimer is arranged as a parallel bundle with threefold symmetry.