The transmembrane domains of hepatitis C virus envelope glycoproteins E1 and E2 play a major role in heterodimerization

Oligomerization of viral envelope proteins is essential to control virus as sembly and fusion. The transmembrane domains (TMDs) of hepatitis C virus en velope glycoproteins El and E2 have been shown to play multiple functions d uring the biogenesis of E1E2 heterodimer. This makes them very unique among known transmembrane sequences. In this report, we used alanine scanning in sertion mutagenesis in the TMDs of El and E2 to examine their role in the a ssembly of E1E2 heterodimer. Alanine insertion within the center of the TMD s of El or E2 or in the N-terminal part of the TMD of El dramatically reduc ed heterodimerization, demonstrating the essential role played by these dom ains in the assembly of hepatitis C virus envelope glycoproteins. To better understand the alanine scanning data obtained for the TMD of El which cont ains GXXXG motifs, we analyzed by circular dichroism and nuclear magnetic r esonance the three dimensional structure of the E1-(350-370) peptide encomp assing the N-terminal sequence of the TMD of El involved in heterodimerizat ion. Alanine scanning results and the three-dimensional molecular model we obtained provide the first framework for a molecular level understanding of the mechanism of hepatitis C virus envelope glycoprotein heterodimerizatio n.