Transmembrane domain of the hepatitis C virus E2 glycoprotein is required for correct folding of the E1 glycoprotein and native complex formation

Hepatitis C virus (HCV) encodes two glycoproteins, E1 and E2, that interact to form both native and aggregated complexes is tissue culture cells. In n ative complexes, E1 and E2 are associated by noncovalent interactions and s uch complexes are considered to constitute the authentic interactions betwe en the proteins. By contrast, the proteins are linked by covalent, disulfid e bonds in aggregated complexes. From studies with a mutant in which cystei ne residues in E1 have been substituted with other amino acids, we show tha t E1 continues to associate with E2, although the migratory patterns of the proteins on gels are consistent with the formation of aggregated complexes . Therefore, such complexes can be stabilized by noncovalent as well as cov alent interactions. To further examine the requirements for native complex formation, segments of foreign glycoproteins were linked to regions of E2. Our data provide direct evidence for the requirement of C-terminal sequence s in E2 that contain the transmembrane domain to permit oxidation of E1 and assembly of a native complex. By contrast, native complexes and oxidized E 1 are not found in the presence of chimeric proteins containing the E2 ecto domain. These data suggest that interaction of E1 with the E2 transmembrane domain is critical for native complex formation. (C) 2001 Academic Press.