FIV env gp95

Feline immunodeficiency virus (FIV) is a lentivirus that affects cats worldwide. From 2.5% up to 4.4% of cats worldwide are infected with FIV. FIV differs taxonomically from two other feline retroviruses, feline leukemia virus (FeLV) and feline foamy virus (FFV), and is more closely related to human immunodeficiency virus (HIV). Within FIV, five subtypes have been identified based on nucleotide sequence differences coding for the viral envelope (env) or polymerase (pol). FIV is the only non-primate lentivirus to cause an AIDS-like syndrome, but FIV is not typically fatal for cats, as they can live relatively healthily as carriers and transmitters of the disease for many years. A vaccine is available although its efficacy remains uncertain. Cats will test positive for FIV antibodies after vaccination.

Full Name

Feline Immunodeficiency Virus Envelope Gp95

Function

The surface protein (SU) attaches the virus to the host cell by binding to its receptor. This interaction triggers the refolding of the transmembrane protein (TM) and is thought to activate its fusogenic potential by unmasking its fusion peptide. Fusion occurs at the host cell plasma membrane (By similarity).

The transmembrane protein (TM) acts as a class I viral fusion protein. Under the current model, the protein has at least 3 conformational states: pre-fusion native state, pre-hairpin intermediate state, and post-fusion hairpin state. During viral and target cell membrane fusion, the coiled coil regions (heptad repeats) assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and target cell membranes. Membranes fusion leads to delivery of the nucleocapsid into the cytoplasm (By similarity).

Biological Process

Viral entry into host cell Source: UniProtKB-KW
Virion attachment to host cell Source: UniProtKB-KW

Cellular Location

Transmembrane protein: Virion membrane; Host cell membrane. It is probably concentrated at the site of budding and incorporated into the virions possibly by contacts between the cytoplasmic tail of Env and the N-terminus of Gag.
Surface protein: Virion membrane; Host cell membrane. The surface protein is not anchored to the viral envelope, but associates with the extravirion surface through its binding to TM. It is probably concentrated at the site of budding and incorporated into the virions possibly by contacts between the cytoplasmic tail of Env and the N-terminus of Gag (By similarity).

Topology

Extracellular: 1-785
Helical: 786-806
Cytoplasmic: 807-856

PTM

Specific enzymatic cleavages in vivo yield mature proteins. Envelope glycoproteins are synthesized as an inactive precursor that is N-glycosylated and processed likely by host cell furin or by a furin-like protease in the Golgi to yield the mature SU and TM proteins. The cleavage site between SU and TM requires the minimal sequence [KR]-X-[KR]-R (By similarity).