GP41

GP41 refers to a protein encoded by the *gp41* gene. In the context of virology, specifically the Human Immunodeficiency Virus (HIV), GP41 is a transmembrane envelope glycoprotein. It is one of the two main glycoproteins found on the surface of the HIV virion, the other being GP120. GP41 is responsible for the fusion of the viral envelope with the host cell membrane, a critical step in the viral entry process.

The GP41 protein is synthesized as a precursor that is cleaved into two subunits. The ectodomain of GP41, which is exposed on the viral surface, is non-covalently associated with GP120. The ectodomain plays a crucial role in mediating the fusion process after GP120 has bound to the host cell receptor (CD4) and a co-receptor (like CCR5 or CXCR4). Following this binding, a conformational change occurs in GP120, exposing the GP41 ectodomain. GP41 then undergoes a series of conformational changes that drive the insertion of its hydrophobic fusion peptide into the host cell membrane, followed by refolding to bring the viral and cellular membranes into close proximity, ultimately leading to fusion and viral entry.

Due to its essential role in viral entry, GP41 is a significant target for antiviral drug development. Inhibitors that block the function of GP41 can prevent HIV from infecting new cells. These drugs, known as fusion inhibitors, represent an important class of antiretroviral therapies. Antibodies targeting GP41 are also being investigated as potential therapeutic or preventative agents.