Question

Describe the structure and maturation of an HIV-1 viron.

Answer 1

The HIV- 1 virion is spherical in shape. it has a diameter of about 100 nanometer.
the virion is delimited by an outer coat - the viral envelope , that surrounds and protects the internal components of the virus and contains the proteins that allows the virus to recognise new host cells.
Inside the virion are viral structural proteins that assemble into a shell, or capsid, that further surrounds and recognise the viral genome.

There are two morphologically distinct forms of the virion called immature and mature. The immature virion is the form that assembles and initiates budding at the plasma membrane of an infected host cell. This form is not capable of transmitting infection.During or immediately after budding, virion reorganizes into the mature form.The mature virion is fully infectious.

Viral maturation is driven by viral PR cleavage of the Gag and Gar- Pro- poly proteins at 10 different sites, ultimately producing the fully processed MA,CA,NC,p6,PR,RT, IN proteins.
Over the course of maturation, these processed proteins rearrange dramatically to create the mature infectious virion, with its characteristic conical core. The MA protein remains associated with the inner leaflet of the viral membrane, forming a discontinuous matrix shell that lacks long range order.The outer capsid shell of core particle is composed of approximately 1200 copies CA proteins and is typically conical.
The capsid approaches the Matrix closely at both ends, particularly at the narrow and which may represent the nucleation site for assembly. The capsid surrounds nucleocapsid, which typically resides at the wide end of the capsid and lack obvious long range order.