The HIV Nef (Negative Regulatory Factor) protein is a 27 to 34 kilodalton multifunctional viral accesorry protein. It is myristoylated at its amino terminus, allowing it to associate with the plasma membrane. One of its functions is to facilitate the activation of host T-cells to provide a favorable environment for virion replication. It also promotes evasion of the infected host cell from cytotoxic T cells.