2 The viral fusion protein leucine-zipper, coiled-coil domain: A target for the discovery of novel antivirals

1994 ◽  
Vol 23 ◽  
pp. 36
Keyword(s):  
Fusion Protein ◽  
Leucine Zipper ◽  
Coiled Coil ◽  
Viral Fusion ◽  
Viral Fusion Protein ◽  
Coiled Coil Domain

scholarly journals Membrane Interactions of the Tick-Borne Encephalitis Virus Fusion Protein E at Low pH

2002 ◽  
Vol 76 (8) ◽  
pp. 3784-3790 ◽  
Author(s):  
Karin Stiasny ◽  
Steven L. Allison ◽  
Juliane Schalich ◽  
Franz X. Heinz
Keyword(s):  
Fusion Protein ◽  
Membrane Binding ◽  
Low Ph ◽  
Encephalitis Virus ◽  
Soluble Form ◽  
Viral Fusion ◽  
Sequence Element ◽  
Viral Fusion Protein ◽  
Tick Borne Encephalitis ◽  
Tick Borne Encephalitis Virus

ABSTRACT Membrane fusion of the flavivirus tick-borne encephalitis virus is triggered by the mildly acidic pH of the endosome and is mediated by envelope protein E, a class II viral fusion protein. The low-pH trigger induces an oligomeric rearrangement in which the subunits of the native E homodimers dissociate and the monomeric subunits then reassociate into homotrimers. Here we provide evidence that membrane binding is mediated by the intermediate monomeric form of E, generated by low-pH-induced dissociation of the dimer. Liposome coflotation experiments revealed that association with target membranes occurred only when liposomes were present at the time of acidification, whereas pretreating virions at low pH in the absence of membranes resulted in the loss of their ability to stably attach to liposomes. With the cleavable cross-linker ethylene glycolbis(succinimidylsuccinate), it was shown that a truncated soluble form of the E protein (sE) could bind to membranes only when the dimers were free to dissociate at low pH, and binding could be blocked by a monoclonal antibody that recognizes the fusion peptide, which is at the distal tip of the E monomer but is buried in the native dimer. Surprisingly, analysis of the membrane-associated sE proteins revealed that they had formed trimers. This was unexpected because this protein lacks a sequence element in the C-terminal stem-anchor region, which was shown to be essential for trimerization in the absence of a target membrane. It can therefore be concluded that the formation of a trimeric form of sE is facilitated by membrane binding. Its stability is apparently maintained by contacts between the ectodomains only and is not dependent on sequence elements in the stem-anchor region as previously assumed.  

Characterization of Two New Imatinib-Responsive Fusion Genes Generated by Disruption of PDGFRB in Eosinophilia-Associated Chronic Myeloproliferative Disorders.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 667-667
Author(s):  
Christoph Walz ◽  
Georgia Metzgeroth ◽  
Claudia Schoch ◽  
Torsten Haferlach ◽  
Rudiger Hehlmann ◽  
...  
Keyword(s):  
Amino Acid ◽  
Fusion Protein ◽  
Tyrosine Kinase ◽  
Coiled Coil ◽  
Myeloproliferative Disorders ◽  
Fusion Genes ◽  
Protein Protein Interaction ◽  
Coiled Coil Domain ◽  
Exon 11

Abstract Fusion genes involving PDGFRA, PDGFRB, FGFR1 and JAK2 are seen in a substantial number of patients with BCR-ABL negative myeloproliferative disorders (MPD) and result in constitutive activation of the corresponding tyrosine kinase moiety. The vast majority of tyrosine kinase fusion partners contain coiled-coil domains or other dimerization motifs properties that are essential for malignant transformation. We have identified two patients presenting with eosinophilia-associated MPD and a t(5;12)(q31;q24) or a complex translocation t(1;5;11) with involvement of 5q31, respectively, suggesting a possible involvement of the PDGFRB gene which is located at chromosome band 5q31–33. 5′-rapid amplification of cDNA ends (5′-RACE) for the t(5;12) identified an in-frame mRNA fusion between ’G protein-coupled receptor kinase interactor 2′ (GIT2) exon 12 at 12q24 and PDGFRB exon 11. GIT2 is a member of the GIT protein family that is extensively alternative spliced in many distinct forms causing its functional diversity. A reciprocal transcript was amplified by RT-PCR with a fusion between PDGFRB exon 10 and GIT2 exon 13. GIT2-PDGFRB is predicted to be translated into a 742 amino acid fusion protein that retains the GIT2 N-terminal protein-protein interaction motif Ankyrin and an Arf GTPase activating protein (ArfGAP) domain fused to the transmembrane and catalytic domain of PDGFRB. The truncated GIT2 protein lacks coiled-coil domains as they are lost in the fusion protein due to the breakpoint within GIT2 intron 12. We therefore speculate that the Ankyrin repeat, which is one of the most common protein-protein interaction motifs in nature, may have replaced the function of a coiled-coil domain offering dimerization properties to the fusion protein. 5′-RACE for the complex t(1;5;11) identified an in-frame mRNA fusion between ’GPI-anchored membrane protein 1′ (GPIAP1) exon 7 at 11p13 and PDGFRB exon 11. Normal GPIAP1 is a cytoplasmic phosphoprotein which plays a mainly uncharacterized role in cellular activation or proliferation. The chimeric mRNA is predicted to encode an 803 amino acid fusion protein retaining the coiled-coil domain of GPIAP1 fused to the transmembrane and catalytic domains of PDGFRB. Both patients have been treated with 400 mg/day imatinib, which is a selective inhibitor of PDGFRB, and achieved rapid complete clinical and hematological remission. Residual GIT2-PDGFRB transcripts could be detected repeatedly during a 17 months follow up in case 1 whereas no follow-up samples have been available for case 2. These data give further evidence that numerous partner genes fuse to PDGFRB in BCR-ABL negative MPDs. In addition, the data demonstrate that cytogenetic analysis is a mandatory technique for the identification of tyrosine kinase fusion genes. In cases with abnormalities of chromosome 5q, a possible involvement of PDGFRB should be screened by adequate FISH and PCR-based techniques. Although their occurrence is rare in general, the identification of these fusion genes is essential for the successful treatment with tyrosine kinase inhibitors.

scholarly journals Role of Metastability and Acidic pH in Membrane Fusion by Tick-Borne Encephalitis Virus

2001 ◽  
Vol 75 (16) ◽  
pp. 7392-7398 ◽  
Author(s):  
Karin Stiasny ◽  
Steven L. Allison ◽  
Christian W. Mandl ◽  
Franz X. Heinz
Keyword(s):  
Influenza Virus ◽  
Fusion Protein ◽  
Membrane Fusion ◽  
Low Ph ◽  
Class I ◽  
Acidic Ph ◽  
Viral Fusion ◽  
Viral Fusion Protein ◽  
Tick Borne Encephalitis ◽  
Tbe Virus

ABSTRACT The envelope protein E of the flavivirus tick-borne encephalitis (TBE) virus is, like the alphavirus E1 protein, a class II viral fusion protein that differs structurally and probably mechanistically from class I viral fusion proteins. The surface of the native TBE virion is covered by an icosahedrally symmetrical network of E homodimers, which mediate low-pH-induced fusion in endosomes. At the pH of fusion, the E homodimers are irreversibly converted to a homotrimeric form, which we have found by intrinsic fluorescence measurements to be more stable than the native dimers. Thus, the TBE virus E protein is analogous to the prototypical class I fusion protein, the influenza virus hemagglutinin (HA), in that it is initially synthesized in a metastable state that is energetically poised to be converted to the fusogenic state by exposure to low pH. However, in contrast to what has been observed with influenza virus HA, this transition could not be triggered by input of heat energy alone and membrane fusion could be induced only when the virus was exposed to an acidic pH. In a previous study we showed that the dimer-to-trimer transition appears to be a two-step process involving a reversible dissociation of the dimer followed by an irreversible trimerization of the dissociated monomeric subunits. Because the dimer-monomer equilibrium in the first step apparently depends on the protonation state of E, the lack of availability of monomers for the trimerization step at neutral pH could explain why low pH is essential for fusion in spite of the metastability of the native E dimer.

scholarly journals Identification and Characterization of the Putative Fusion Peptide of the Severe Acute Respiratory Syndrome-Associated Coronavirus Spike Protein

2005 ◽  
Vol 79 (11) ◽  
pp. 7195-7206 ◽  
Author(s):  
Bruno Sainz ◽  
Joshua M. Rausch ◽  
William R. Gallaher ◽  
Robert F. Garry ◽  
William C. Wimley
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Fusion Protein ◽  
Protein A ◽  
Fusion Peptide ◽  
Class I ◽  
Viral Fusion ◽  
Fusion Peptides ◽  
Viral Fusion Protein ◽  
Ww Ii ◽  
Heptad Repeats

ABSTRACT Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) is a newly identified member of the family Coronaviridae and poses a serious public health threat. Recent studies indicated that the SARS-CoV viral spike glycoprotein is a class I viral fusion protein. A fusion peptide present at the N-terminal region of class I viral fusion proteins is believed to initiate viral and cell membrane interactions and subsequent fusion. Although the SARS-CoV fusion protein heptad repeats have been well characterized, the fusion peptide has yet to be identified. Based on the conserved features of known viral fusion peptides and using Wimley and White interfacial hydrophobicity plots, we have identified two putative fusion peptides (SARSWW-I and SARSWW-II) at the N terminus of the SARS-CoV S2 subunit. Both peptides are hydrophobic and rich in alanine, glycine, and/or phenylalanine residues and contain a canonical fusion tripeptide along with a central proline residue. Only the SARSWW-I peptide strongly partitioned into the membranes of large unilamellar vesicles (LUV), adopting a β-sheet structure. Likewise, only SARSWW-I induced the fusion of LUV and caused membrane leakage of vesicle contents at peptide/lipid ratios of 1:50 and 1:100, respectively. The activity of this synthetic peptide appeared to be dependent on its amino acid (aa) sequence, as scrambling the peptide rendered it unable to partition into LUV, assume a defined secondary structure, or induce both fusion and leakage of LUV. Based on the activity of SARSWW-I, we propose that the hydrophobic stretch of 19 aa corresponding to residues 770 to 788 is a fusion peptide of the SARS-CoV S2 subunit.

scholarly journals Reevaluating Herpes Simplex Virus Hemifusion

2010 ◽  
Vol 84 (22) ◽  
pp. 11814-11821 ◽  
Author(s):  
Julia O. Jackson ◽  
Richard Longnecker
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Fusion Protein ◽  
Membrane Fusion ◽  
Fusion Proteins ◽  
Fusion Pore ◽  
Viral Fusion ◽  
Viral Fusion Protein ◽  
Viral Fusion Proteins ◽  
Simplex Virus

ABSTRACT Membrane fusion induced by enveloped viruses proceeds through the actions of viral fusion proteins. Once activated, viral fusion proteins undergo large protein conformational changes to execute membrane fusion. Fusion is thought to proceed through a “hemifusion” intermediate in which the outer membrane leaflets of target and viral membranes mix (lipid mixing) prior to fusion pore formation, enlargement, and completion of fusion. Herpes simplex virus type 1 (HSV-1) requires four glycoproteins—glycoprotein D (gD), glycoprotein B (gB), and a heterodimer of glycoprotein H and L (gH/gL)—to accomplish fusion. gD is primarily thought of as a receptor-binding protein and gB as a fusion protein. The role of gH/gL in fusion has remained enigmatic. Despite experimental evidence that gH/gL may be a fusion protein capable of inducing hemifusion in the absence of gB, the recently solved crystal structure of HSV-2 gH/gL has no structural homology to any known viral fusion protein. We found that in our hands, all HSV entry proteins—gD, gB, and gH/gL—were required to observe lipid mixing in both cell-cell- and virus-cell-based hemifusion assays. To verify that our hemifusion assay was capable of detecting hemifusion, we used glycosylphosphatidylinositol (GPI)-linked hemagglutinin (HA), a variant of the influenza virus fusion protein, HA, known to stall the fusion process before productive fusion pores are formed. Additionally, we found that a mutant carrying an insertion within the short gH cytoplasmic tail, 824L gH, is incapable of executing hemifusion despite normal cell surface expression. Collectively, our findings suggest that HSV gH/gL may not function as a fusion protein and that all HSV entry glycoproteins are required for both hemifusion and fusion. The previously described gH 824L mutation blocks gH/gL function prior to HSV-induced lipid mixing.

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