Glycoprotein G (G)

Glycoprotein G is a crucial spike protein found on the surface of many enveloped viruses. Its primary function is to act as the viral "key," initiating infection by attaching to specific receptor molecules on the host cell surface. This receptor-binding step is essential for determining the virus's host range and tissue tropism—which species and which cells within the body it can infect. Furthermore, Glycoprotein G is often a major antigen, meaning it is a primary target recognized by the host's immune system. Antibodies generated against it can block receptor attachment, making it a critical focal point for the development of vaccines and therapeutic antibodies.

The Glycoprotein G of Nipah virus (NiV-G) is a master determinant of its severe pathogenicity. Unlike some viral attachment proteins, NiV-G does not directly cause membrane fusion. Instead, it specifically and with high affinity binds to ephrin-B2 and ephrin-B3 receptors, which are abundantly present on the surface of neurons and endothelial cells lining blood vessels. This precise binding explains NiV's devastating neurotropism and its ability to cause fatal encephalitis and vasculitis. The attachment of NiV-G to its receptor triggers a conformational change in the separate viral Fusion (F) protein, which then drives the merging of the viral and host cell membranes. As the main target for neutralizing antibodies, NiV-G is the cornerstone of vaccine design.