The basis for structural architecture of the envelope of hantaviruses, family Bunyaviridae, is in this report systematically studied by the interactions of the two glycoproteins Gn and Gc and their respective disulphide-bridge mediated homo- and heteromeric oligomerizations. In virion extracts Gn and Gc associated in both homo- and hetero-oligomers which were, at least partially, thiol-bridge mediated. Due to strong homo-oligomerization the hetero-oligomers of Gn and Gc are likely to be mediated by homo-oligomeric subunits. A reversible pH-induced disappearance of a neutralizing epitope in Gc and dissociation of the Gn-Gc complex at pH below 6.2, provide proteochemical evidence for fusogenicity of Gc. Incomplete inactivation of virions at acidic pH tell tales that additional factors are required for hantavirus fusion as in the case of pestiviruses of Flaviviridea. By resemblances to class II fusion proteins a structure model was created of hantavirus Gc using Semliki Forest virus E1 protein as the template. In total, ten binding regions for Gn were found by peptide scanning of which five represent homotypic (GnI-V) and five heterotypic (GcI-V) interaction sites that we assign as intra- and inter-spike connections, respectively. In conclusion, the glycoprotein associations were compiled to a model wherein the surface of hantaviruses is formed of homotetrameric Gn complexes interconnected with Gc homodimers. This organization would create the grid-like surface pattern described earlier for hantaviruses in negatively-stained electron microscopy specimens.
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