Respiratory Syncytial Virus (RSV) Fusion (F) Glycoprotein is a Class I viral fusion protein. The Glycoprotein 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 heptad repeat regions 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, directs fusion of viral and cellular membranes leading to delivery of the nucleocapsid into the cytoplasm. This fusion is pH independent and occurs directly at the outer cell membrane. The trimer of F1-F2 (protein F) interacts with glycoprotein G at the virion surface. Upon binding of G to heparan sulfate, the hydrophobic fusion peptide is unmasked and interacts with the cellular membrane, inducing the fusion between host cell and virion

CD13/Aminopeptidase-N [APN/514]

CD13, also known as aminopeptidase N, was originally identified as a cell surface glycoprotein expressed by cells of granulocytic and monocytic lineages at various differentiation stages. Sequence comparisons showed that the cDNA sequence of CD13 is identical to aminopeptidase N (APN), a prominent membrane-anchored metallopeptidase expressed by the brush borders of the smallintestinal and renal microvillar membrane, and also in other plasma membranes. Human APN is a receptor for one strain of human coronavirus that is an important cause of upper respiratory tract infections. Human CD13 may also mediate HCMV infection by a process that increases binding, but not its enzymatic domain. CD13 has been used as a myeloid marker. The antibody labels leukemic blasts in acute myeloid leukemia (AML) and is helpful in identifying AML subtype M0 acute lymphoid leukemia (ALL). Additionally, CD13 is a sensitive but not entirely specific marker for anaplastic lymphoma kinase positive (ALK+) anaplastic large cell lymphomas (ALCLs). CD13 is also expressed in nonhematopoietic cells including fibroblasts, bone marrow stromal cells, osteoclasts and epithelial cells. A canalicular staining pattern of CD13 in hepatocellular carcinoma (HCC) is useful in differentiation between HCC and non- HCC in liver.

CD13/Aminopeptidase-N [APN/514]