a-type antiviral protein

Interferon‑alpha beta receptor 1 (IFN‑ alpha beta R1), also known as IFNAR1, are present in all tissues and even on the surface of most IFN-resistant cells. Isoform 1, isoform 2 and isoform 3 are expressed in the IFN-alpha sensitive myeloma cell line U266B1. Isoform 2 and isoform 3 are expressed in the IFN-alpha resistant myeloma cell line U266R. Isoform 1 is not expressed in IFN-alpha resistant myeloma cell line U266R. It interacts with STAT1 and STAT2, the interaction requires its phosphorylation at Tyr-466. It also interacts with FBXW11, the substrate recognition component of a SCF (SKP1-CUL1-F-box protein) E3 ubiquitin-protein ligase complex.

Expression system: E. coli
Length: 20-164, Full Length of Mature Protein
Activity: Not Tested

Expression system: E. coli
Length: 24-166, Full Length of Mature Protein
Activity: Not Tested

Expression system: E. coli
Length: 1-176, Partial
Activity: Not Tested

Expression system: E. coli
Length: 1-237, Full Length
Activity: Not Tested

Expression system: P. pastoris (Yeast)
Length: 24-166, Full Length of Mature Protein
Activity: Not Tested

Expression system: E. coli
Length: 1-470, Full Length
Activity: Not Tested

Expression system: Baculovirus Insect Cells
Length: 1-470, Full Length
Activity: Not Tested

Expression system: HEK293 Cells
Length: 39-207, Partial
Activity: Not Tested

Replication of severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) requires proteolytic processing of the replicase polyprotein by two viral cysteine proteases, a chymotrypsin-like protease (3CLpro) and a papain-like protease (PLpro). These proteases are important targets for development of antiviral drugs that would inhibit viral replication and reduce mortality associated with outbreaks of SARS-CoV. PLpro is a cysteine protease located within the non-structural protein 3 (NS3) section of the viral polypeptide. PLPro activity is required to process the viral polyprotein into functional, mature subunits; specifically, PLPro cleaves a site at the amino-terminus of the viral replicase region. In addition to its role in viral protein maturation, PLPro possesses a deubiquitinating and deISGylating activity. In vivo, this protease antagonizes innate immunity by inhibiting IRF3-induced production of type I interferons.

Cystatin-S, also known as Cystatin-4, Salivary acidic protein 1, Cystatin-SA-III and CST4, is a secreted protein which belongs to thecystatin family. Cystatin-4 CST4 is expressed in submandibular and sublingual saliva but not in parotid saliva (at protein level). It is also expressed in saliva, tears, urine and seminal fluid. The cystatin superfamily encompasses proteins that contain multiple cystatin-like sequences. Some of the members are active cysteine protease inhibitors, while others have lost or perhaps never acquired this inhibitory activity. There are three inhibitory families in the superfamily, including the type 1 cystatins (stefins), type 2 cystatins and the kininogens. The type 2 cystatin proteins are a class of cysteine proteinase inhibitors found in a variety of human fluids and secretions. Cystatin-4 CST4 strongly inhibits papain and ficin, partially inhibits stem bromelain and bovine cathepsin C, but does not inhibit porcine cathepsin B or clostripain. Papain is inhibited non-competitively. Cystatin-4 CST4 is an S-type cystatin, based on its high level of expression in saliva, tears and seminal plasma. The specific role in these fluids is unclear but antibacterial and antiviral activity is present, consistent with a protective function.

STAT1 is a member of the STAT protein family. In response to cytokines and growth factors, STAT family members are phosphorylated by the receptor-associated kinases, and then form homo- or heterodimers that translocate to the cell nucleus where they act as transcription activators. STAT1 can be activated by various ligands, including interferon-alpha, interferon-gamma, EGF, PDGF and IL6. It is a signal transducer and transcription activator that mediates cellular responses to interferons (IFNs), cytokine KITLG SCF and other cytokines and growth factors. The phosphorylated STATs dimerize, associate with ISGF3G IRF-9 to form a complex termed ISGF3 transcription factor, that enters the nucleus. ISGF3 binds to the IFN stimulated response element (ISRE) to activate the transcription of interferon-stimulated genes, which drive the cell in an antiviral state. In response to type II IFN (IFN-gamma), STAT1 is tyrosine- and serine-phosphorylated. It then forms a homodimer termed IFN-gamma-activated factor (GAF), migrates into the nucleus and binds to the IFN gamma activated sequence (GAS) to drive the expression of the target genes, inducing a cellular antiviral state. STAT1 becomes activated in response to KITLG SCF and KIT signaling and may mediate cellular responses to activated FGFR1, FGFR2, FGFR3 and FGFR4. Defects in STAT1 can cause STAT1 deficiency complete and familial candidiasis type 7.

B18R is a type I interferon (IFN)-binding protein, which is encoded by the B18R open reading frame in the WR (Western Reserve) strain of vaccinia virus. It is also known as B19R in the Copenhagen strain of Vaccinia. B18R exists in a soluble and a membrane-bound form. As a type I IFN receptor, B18R has a broad species specificity. It has high affinity for human IFN-alpha and also binds rabbit, bovine, rat, pig, and mouse IFN-alpha and IFN-beta. It has been shown that secreted B18R binds to uninfected and infected cells. It presents at the cell surface and protects cells from the antiviral state induced by IFN-alpha and IFN-beta. Binding of soluble recombinant B18R protects cultured cells from IFN and allows vaccinia virus replication.

Expression system: E. coli
Length: 24-166, Full Length of Mature Protein
Activity: Cell Activity