Retroviral virion without labels
A schematic retroviral virion (excluding labels). All retroviruses share a similar basic virion structure and genome organisation. Retroviral virions range from 80-100 nm in diameter. They have an internal protein core that contains the viral genomic RNA and is surrounded by a lipid envelope. The core structure is composed of matrix (MA), capsid (CA) and nucleocapsid (NC) structural proteins and contains reverse transcriptase (RT), integrase (IN), and protease (PR) enzymes. The viral envelope is derived from the host cell, and is formed when the virus particle buds from host cell plasma membrane in which viral glycoproteins are inserted. The glycoproteins are composed of transmembrane (TM) and surface (SU) subunits linked by disulphide bonds.