Heterodimerization of HCV envelope glycoproteins within the membrane
The hepatitis C virus (HCV) is a world-wide health concern, afflicting 3% of the world population. Currently available treatments suffer from undesirable side-effects and unacceptable response levels, emphasizing the importance of new paradigms in HCV therapy. Mandatory for invasion of cells by the virus is a heterodimerization of two envelope glycoproteins, E1 and E2, which interact between themselves and with cell-surface receptors to mediate membrane fusion followed by cell entry. Particularly, mutations occurring in their membrane spanning (transmembrane, or TM) have been shown to reduce infectivity. We have focused on the interaction between the TM-regions of the two glycoproteins, with the ultimate objective of determining the structure of the heterodimer and providing a roadmap for drug design efforts targeting the E1/E2 association. Synthesis and heterologous expression of membrane-spanning peptides is notoriously difficult because of their tendency to aggregate. We succeeded in purifying and labeling E1-TM and E2-TM, short (40-50 residue) peptides, and determining their global fold in stabilizing phospholipid micelles. However, both peptides contain functionally critical charged residues in their sequence, which in micelles distort the helical structure by ‘snorkeling’ out into the headgroup perimeter. For an accurate structure we will need to form the dimer, a kinetically and thermodynamically unfavorable process. We aim to covalently link the two peptides and incorporate them together into phospholipid bicelles, thus emulating their native surroundings and obtaining a correct structure for this complex.
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Zazrin, H.; Shaked, H.; Chill, J.H. Architecture of the hepatitis C virus E1 glycoprotein transmembrane domain studied by NMR. BBA-Biomembranes 2014, 1838(3), 784-792.
Elazari-Shalom, H.;† Zazrin-Grynspan, H.;† Shaked, H.; Chill, J.H. An NMR study of the transmembrane domain of hepatitis C virus E2 glycoprotein. BBA-Biomembranes, 2014, 1838(11):2919-2128.†Equal contribution.