"[Glycoprotein G2]: Homotrimer. Interacts with the stable signal peptide. In pre-fusion state, G2 homotrimers bind G1 homotrimers via ionic interactions. Part of the GP complex (GP-C) together with glycoprotein G1 and the stable signal peptide. Acidification in the endosome triggers rearrangements, which ultimately leads to a 6 helix bundle formed by the two heptad repeat domains (HR1 and HR2) in post-fusion state. The GP-complex interacts with protein Z, which interacts with ribonucleocapsid; these interactions may induce virion budding."xsd:string