Preliminary experiments gave an approx 30kDa band in Human Placenta lysates after 1µg/ml antibody staining. Please note that currently we cannot find an explanation in the literature for the band we observe given the calculated size of 67.9kDa according to NP_001007254.2. The 30kDa band was successfully blocked by incubation with the immunizing peptide. We would appreciate any feedback from people in the field - have any results been reported with other antibodies/lysates? Have any further splice variants/modified forms been reported?
, corresponding to internal sequence amino acids 313-323 of Human HERV (NP_001007254.2)
Retroviral envelope proteins mediate receptor recognition and membrane fusion during early infection. Endogenous envelope proteins may have kept, lost or modified their original function during evolution. This endogenous envelope protein has retained its original fusogenic properties and participates in trophoblast fusion during placenta morphogenesis. SU mediates receptor recognition. This interaction triggers the refolding of the transmembrane protein (TM) and is thought to activate its fusogenic potential by unmasking its fusion peptide (By similarity). Seems to recognize the type D mammalian retrovirus receptors SLC1A4 and SLC1A5, as it induces fusion of cells expressing these receptors in vitro. 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 membranes.
Expressed at higher level in placental syncytiotrophoblast. Expressed at intermediate level in testis. Seems also to be found at low level in adrenal tissue, bone marrow, breast, colon, kidney, ovary, prostate, skin, spleen, thymus, thyroid, brain and trachea. Both mRNA and protein levels are significantly increased in the brain of individuals with multiple sclerosis, particularly in astrocytes and microglia.
Belongs to the gamma type-C retroviral envelope protein family. HERV class-I W env subfamily.
In placenta, detected at higher level during early pregnancy and at lower level during late pregnancy.
The cytoplasmic region is essential for the fusiogenic function. The 17 amino acids long immunosuppressive region is present in many retroviral envelope proteins. Synthetic peptides derived from this relatively conserved sequence inhibit immune function in vitro and in vivo.
Specific enzymatic cleavages in vivo yield mature proteins. Envelope glycoproteins are synthesized as a inactive precursor that is heavily N-glycosylated and processed likely by furin 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. The intracytoplasmic tail cleavage by the viral protease that is required for the fusiogenic activity of some retroviruses envelope proteins seems to have been lost during evolution. The CXXC motif is highly conserved across a broad range of retroviral envelope proteins. It is thought to participate in the formation of a labile disulfide bond possibly with the CX6CC motif present in the transmembrane protein. Isomerization of the intersubunit disulfide bond to an SU intrachain disulfide bond is thought to occur upon receptor recognition in order to allow membrane fusion.
Cell membrane; Virion and Cell membrane. The surface protein is not anchored to the membrane, but localizes to the extracellular surface through its binding to TM.