Domains and segments nomenclature used in the text.

Root mean square deviation (RMSD) and number of superimposable alpha carbons (Cα) are reported between indicated domains. As the distal (fusion loop-containing) part of FD is the most flexible part in all structures, we defined a “FD upper part” which was used to calculate the RMSD between VSV and CHAV-Gth. We also defined a PHD core corresponding to the 79 residues (out of 90) in CHAV-G which are in structurally equivalent positions in VSV-G. The RMSD between the two (PHD core + FD upper part) is not significantly different from the value obtained for the PHD core alone. This indicates that the relative orientation of the two domains is the same in both proteins.Domains and segments nomenclature used in the text.