A protein coevolution method uncovers critical features of the Hepatitis C Virus fusion mechanism
Fig 6
A dialog between E1 residues and the BL modulates virus entry and fusion.
(A) Representation of the gt2 fusion cluster 5 (orange; dotted circle and linked by a bold line) as a putative mediator of E2 BL rearrangements and fusogenic conformational changes. Putative movements of the E2 BL are indicated by dotted double arrows. Rotation angles of the E2core structure and black cross are indicated as in Fig 3B. (B) Regions of interest to study the role of the cluster 5 (orange) and design of the gt2 chimera. Three regions were defined as cluster 5 blocks. One is located on E1 (30 aa; Region 1) and two are located in E2 BLd (Region 2: E2 408–436, N terminal region; Region 3: E2 437–456, C terminal region). (C-D) A dialog between E1 and the BL domain regulates virus entry. Infectious titers of HCVpp (GFP i.u./ml, C) and HCVcc (FFU/ml, D) viral particles harboring J6 (black), 2b1 (white) and J6/2b1 E1E2 chimera. Swapped regions (1, 2 or 3) are represented by white (2b1) or black (J6) boxes inserted into J6 or 2b1 linear representations, respectively (bottom). Infectious titers were quantified 72h (HCVpp) or 4 days (HCVcc) post infection of Huh7.5. (mean ± SD; n = 4); *p<0.05.; ns non-significant. (E-F) A dialog between E1 and the BL domain regulates membrane fusion. Cell-cell fusion induced by the different E1E2 chimera (as described in Fig 5J). HANA (Influenza Hemagglutinin-Neuraminidase) envelope glycoproteins were used as positive control. Data are presented as relative light unit (RLU) at pH5 (E) or as percentage of fusion (F) where pH7 RLU is considered as 100% fusion rate for each chimera (mean ± SD; n = 3); *p<0.05, **p<0.01, ***p<0.001 ns non-significant. For panel (F), statistical significances were determined for each experimental condition versus control condition (100%).