Cell membrane Complex Enzyme Eukaryotic cell or cell component Microbe-host cell complex Microorganism or its component Other Other -- ion Pathway or action Protein Protein or gene Protein or gene complex Protein or protein complex Bacterial membrane or virus envelope Cell membrane Cytoplasm Eukaryotic cell or cell component Extracellular Golgi Golgi membrane Intercellular Intracellular Mitochondria Nucleocapsid/Cytoplasm Organelle Organelle -- Cell membrane Organelle -- Endoplasmic reticulum Organelle -- ER Organelle -- Golgi Organelle -- Golgi membrane Organelle -- Nucleus Organelle -- Phagolysosome Organelle -- Phagosome Organelle -- Ribosome Other Phagolysosome Phagosome Chaperone Defense, immunity protein Enzyme Enzyme activator Enzyme inhibitor Genomic S segment Infection Ligand binding or carrier Motor Nucleic acid binding Other Signal transducer Toxicity Transcription factor binding Transcription regulation Transporter Unknown IC Inferred by Curator IDA Inferred from Direct Assay IEA Inferred from Electronic Annotation IEP Inferred from Expression Pattern IGI Inferred from Genetic Interaction IMP Inferred from Mutant Phenotype IPI Inferred from Physical Interaction ISS Inferred from Sequence or Structural Similarity NAS Non-traceable Author Statement ND No biological Data available RCA inferred from Reviewed Computational Analysis TAS Traceable Author Statement NR Not Recorded Volchkov VE, Volchkova VA, Stroher U, Becker S, Dolnik O, Cieplik M, Garten W, Klenk HD, Feldmann H Virology Proteolytic processing of Marburg virus glycoprotein 20001 10683320 PubMed Bavari S, Bosio CM, Wiegand E, Ruthel G, Will AB, Geisbert TW, Hevey M, Schmaljohn C, Schmaljohn A, Aman MJ The Journal of experimental medicine Lipid raft microdomains: a gateway for compartmentalized trafficking of Ebola and Marburg viruses 20024 11877482 PubMed Becker S, Klenk HD, Muhlberger E Virology Intracellular transport and processing of the Marburg virus surface protein in vertebrate and insect cells 19961 8918541 PubMed Sanger C, Muhlberger E, Ryabchikova E, Kolesnikova L, Klenk HD, Becker S Journal of virology Sorting of Marburg virus surface protein and virus release take place at opposite surfaces of infected polarized epithelial cells 2001 11152500 PubMed Becker S and Muhlberger E Marburg and Ebola viruses Co- and posttranslational modifications and functions of Marburg virus proteins. 1999 Modrof J, Moritz C, Kolesnikova L, Konakova T, Hartlieb B, Randolf A, Muhlberger E, Becker S Virology Phosphorylation of Marburg virus VP30 at serines 40 and 42 is critical for its interaction with NP inclusions 200115 11504552 PubMed Kolesnikova L, Bugany H, Klenk HD, Becker S Journal of virology VP40, the matrix protein of Marburg virus, is associated with membranes of the late endosomal compartment 2002 11799178 PubMed Huang Y, Xu L, Sun Y, Nabel GJ Molecular cell The assembly of Ebola virus nucleocapsid requires virion-associated proteins 35 and 24 and posttranslational modification of nucleoprotein 2002 12191476 PubMed Peters CJ, Sanchez A, Rollin PE, Ksiazek TG, and Murphy FA Field's Virology Third Edition Volume 1 Filoviridae: Marburg and Ebola Viruses 1996 Sanger C, Muhlberger E, Lotfering B, Klenk HD, Becker S Virology The Marburg virus surface protein GP is phosphorylated at its ectodomain 200230 12033762 PubMed Muhlberger E, Weik M, Volchkov VE, Klenk HD, Becker S Journal of virology Comparison of the transcription and replication strategies of marburg virus and Ebola virus by using artificial replication systems 1999 9971816 PubMed Kolesnikova L, Muhlberger E, Ryabchikova E, Becker S Journal of virology Ultrastructural organization of recombinant Marburg virus nucleoprotein: comparison with Marburg virus inclusions 2000 10729166 PubMed Lotfering B, Muhlberger E, Tamura T, Klenk HD, Becker S Virology The nucleoprotein of Marburg virus is target for multiple cellular kinases 19991 10049821 PubMed Feldmann H and Kiley MP Marburg and Ebola viruses Classification, structure, and replication of filoviruses 1999 Bray M, Paragas J Antiviral research Experimental therapy of filovirus infections 2002 11888653 PubMed Feldmann H, Volchkov VE, Volchkova VA, Stroher U, Klenk HD The Journal of general virology Biosynthesis and role of filoviral glycoproteins 2001 11714958 PubMed GP Function: Ligand binding or carrier. Cell entry is presumably mediated by GP (Feldmann and Kiley, 1999). Each molecule in the trimeric GP is composed of an external segment, GP1, which is linked by a disulfide bond to a transmembrane unit, GP2 (Bray and Paragas, 2002). Several groups have demonstrated independently that the transmembrane glycoprotein of filoviruses mediates receptor binding and subsequent fusion with susceptible cells (Feldmann et al., 2001).(Feldmann et al., 2001)(Bray et al., 2002)(Feldmann2) Cell membrane receptor Function: Ligand binding or carrier. There is evidence that Marburg virus uses the asialoglycoprotein receptor to infect hepatocytes. For Ebola virus, it was suggested that integrins, especially the Beta1 group, might interact with the glycoprotein and perhaps be involved in entry into the cells. More recent studies indicate that the folate receptor-alpha serves as a cofactor for cellular entry by Marburg and Ebola viruses (Feldmann et al., 2001).(Feldmann et al., 2001) Attached virus Function: . Replication begins with the attachment of the virion to a cell-surface receptor, which may be the alpha-folate receptor. After binding, the virus enters the cell through receptor-mediated endocytosis (Bray and Paragas, 2002).(Bray et al., 2002) Fused virus Function: . Fusion of the viral envelope with the cellular endosomal membrane releases the RNP into the cytoplasm (Bray and Paragas, 2002). Fusion activity has never been demonstrated experimentally. Early post-infection filovirus particles are associated with coated pits along the plasma membrane, indicating endocytosis as a possible mechanism for entry (Feldmann et al., 2001). Recently, it was shown that the coiled-coil motif of GP2 plays an important role in facilitating the entry of Ebola virus. For Marburg virus, a similar putative fusion domain can be found at a distance of 91 amino acids from the cleavage site (Feldmann et al., 2001).(Bray et al., 2002)(Feldmann et al., 2001) Uncoated virus Function: . Virus entry is probably receptor-mediated followed by fusion and uncoating, two steps which have not yet been examined (Feldmann and Kiley, 1999).(Feldmann2) Replication complex Function: . The ribonucleoprotein (RNP) complex in the virion core, made up of the RNA genome and its encapsidating proteins, VP30 and NP, is linked by matrix proteins to the glycoprotein (GP)-bearing lipid envelope derived from the host cell membrane (Bray and Paragas, 2002). Two other proteins present in lower copy number within the virion, VP35 and the RNA-dependent RNA polymerase, or L protein, associate with VP30 and NP to make up the Ebola replication complex (Bray and Paragas, 2002). Genomes of filoviruses consist of a single negative-stranded linear RNA molecule. The RNA is noninfectious, does not contain a poly A tail, and upon entry into the cytoplasm of host cells is transcribed to generated polyadenylated subgenomic mRNA species (Feldmann and Kiley, 1999). The Marburg virus RNA is of negative polarity and encodes seven structural proteins, whose genes are organized in the following linear order: 3' NP, VP35, VP40, GP, VP30, VP24, L 5' (Lotfering et al., 1999). Viral reproduction takes place in the cytoplasm (Kolesnikova et al., 2000).(Bray et al., 2002)(Feldmann2)(Lotfering et al., 1999)(Kolesnikova et al., 2000) NP mRNA Function: . Transcription by the viral RNA-dependent RNA polymerase initiates at the 3' end of the genome, resulting in synthesis of a leader RNA and seven polyadenylated mRNAs. Accumulation of the first two proteins encoded at the 3' end of the genome (NP and VP35) in some way triggers a switch to production of full-length, positive-sense `antigenomes', which serve, in turn, as templates for genome synthesis (Bray and Paragas, 2002). The nucleoprotein (NP) is encoded by gene 1 at the extreme 3' end of the linear unsegmented RNA genome (Feldmann and Kiley, 1999).(Bray et al., 2002)(Feldmann2) VP35 mRNA Function: . Transcription by the viral RNA-dependent RNA polymerase initiates at the 3' end of the genome, resulting in synthesis of a leader RNA and seven polyadenylated mRNAs. Accumulation of the first two proteins encoded at the 3' end of the genome (NP and VP35) in some way triggers a switch to production of full-length, positive-sense `antigenomes', which serve, in turn, as templates for genome synthesis (Bray and Paragas, 2002). Virion structural protein 35 (VP35) is encoded by gene 2 (Feldmann and Kiley, 1999).(Bray et al., 2002)(Feldmann2) VP40 mRNA Function: . Virion structural protein 40 (VP40) of filoviruses is encoded by gene 3 (Feldmann and Kiley, 1999).(Feldmann2) GP mRNA Function: . The glycoprotein of Marburg virus is transcribed from a single open reading frame (Muhlberger et al., 1999). The GP gene is 2,844 nucleotides in length and encodes a protein of 681 amino acids. In contrast to Ebola virus where the virion-associated surface protein is only expressed after mRNA editing, Marburg virus GP is encoded by a single open reading frame (Sanger et al., 2001). GP is encoded by gene 4 of the genome, is the only glycosylated structural protein of virions (Feldmann and Kiley, 1999). The GP is the sole structural protein that makes up the virion surface spikes that mediate virus entry into susceptible host cells through receptor binding (Peters et al., 1996).(Muhlberger et al., 1999)(Sanger et al., 2002)(Feldmann2)(Peters) VP30 mRNA Function: . Virion structural protein 30 (VP30) is encoded by gene 5 of filoviruses and is intimately associated with the RNP complex (Feldmann and Kiley, 1999).(Feldmann2) VP24 mRNA Function: . Virion structural protein 24 (VP24) is encoded by gene 6 of filoviruses (Feldmann and Kiley, 1999). Recent studies with Ebola virus have demonstrated that cotransfection of 293T cells with NP, VP35, and VP24 supported capsid formation, and omission of any one of these three genes abolished the effect, demonstrating that they are necessary and sufficient for viral particle formation (Huang et al., 2002).(Feldmann2)(Huang et al., 2002) L mRNA Function: . The large (L) protein is encoded at the 5' end of the linear genome (Feldmann and Kiley, 1999).(Feldmann2) Positive sense genome Function: . Transcription by the viral RNA-dependent RNA polymerase initiates at the 3' end of the genome, resulting in synthesis of a leader RNA and seven polyadenylated mRNAs. Accumulation of the first two proteins encoded at the 3' end of the genome (NP and VP35) in some way triggers a switch to production of full-length, positive-sense `antigenomes', which serve, in turn, as templates for genome synthesis (Bray and Paragas, 2002).(Bray et al., 2002) Negative sense genome Function: . Transcription by the viral RNA-dependent RNA polymerase initiates at the 3' end of the genome, resulting in synthesis of a leader RNA and seven polyadenylated mRNAs. Accumulation of the first two proteins encoded at the 3' end of the genome (NP and VP35) in some way triggers a switch to production of full-length, positive-sense `antigenomes', which serve, in turn, as templates for genome synthesis (Bray and Paragas, 2002).(Bray et al., 2002) NP protein Function: . Three of the four nucleocapsid proteins, NP, VP35, and L, are sufficient to support replication and transcription of an Marburg virus-specific monocistronic minigenome (Muhlberger et al., 1999). Encapsidation of the genomic RNA by the major nucleocapsid protein (NP) is presumed to be the first step in the assembly process of Marburg virus nucleocapsid (Kolesnikova et al., 2000). Among the proteins of the Marburg virus nucleocapsid complex, only NP has the potential to self-assemble into large aggregates when it is expressed in the absence of other viral proteins (Kolesnikova et al., 2000).Transcription by the viral RNA-dependent RNA polymerase initiates at the 3' end of the genome, resulting in synthesis of a leader RNA and seven polyadenylated mRNAs. Accumulation of the first two proteins encoded at the 3' end of the genome (NP and VP35) in some way triggers a switch to production of full-length, positive-sense `antigenomes', which serve, in turn, as templates for genome synthesis (Bray and Paragas, 2002).NP is the primary structural protein associates with filovirus nucleocapsids (Peters et al., 1996). Recent studies have demonstrated that cotransfection of 293T cells with NP, VP35, and VP24 supported capsid formation, and omission of any one of these three genes abolished the effect, demonstrating that they are necessary and sufficient for viral particle formation (Huang et al., 2002).(Muhlberger et al., 1999)(Kolesnikova et al., 2000)(Bray et al., 2002)(Peters)(Huang et al., 2002) VP35 protein Function: . Three of the four nucleocapsid proteins, NP, VP35, and L, are sufficient to support replication and transcription of an Marburg virus-specific monocistronic minigenome (Muhlberger et al., 1999). There is accumulating evidence that the filovirus VP35 is homologous to the P proteins of other Mononegavirales. First, it was observed previously that Ebola and Marburg virus VP35 are components of the nucleocapsid complex; second, VP35 is essential for replication and transcription of both viruses; third, interaction between NP and VP35 (first and second gene product) parallels interaction between N (NP) and P of paramyxo-, rhabdo-, and borna viruses. It is therefore proposed to further designate VP35 of the Filoviridae as P(Muhlberger et al., 1999). Transcription by the viral RNA-dependent RNA polymerase initiates at the 3' end of the genome, resulting in synthesis of a leader RNA and seven polyadenylated mRNAs. Accumulation of the first two proteins encoded at the 3' end of the genome (NP and VP35) in some way triggers a switch to production of full-length, positive-sense `antigenomes', which serve, in turn, as templates for genome synthesis (Bray and Paragas, 2002).Recent studies have demonstrated that cotransfection of 293T cells with NP, VP35, and VP24 supported capsid formation, and omission of any one of these three genes abolished the effect, demonstrating that they are necessary and sufficient for viral particle formation (Huang et al., 2002).(Muhlberger et al., 1999)(Bray et al., 2002)(Huang et al., 2002) VP40 protein Function: . Between the nucleocapsid and the viral envelope, Marburg virus particles contain two proteins, VP24 and the highly abundant VP40, whose function is not yet elucidated. However, the position of VP40 in the genome (third gene), its hydrophobicity, and its abundance within the virions suggest that VP40 represents a homologue of the matrix proteins of other nonsegmented negative-strand RNA viruses (Kolesnikova et al., 2002). VP40 has been identified in viral inclusions, associated with individual nucleocapsids, and in the foci of viral budding. Additionally, VP40 has been detected in clusters of intracellular membranes and in plasma membrane protrusions. When the localization of recombinant VP40 was investigated, it was found to be firmly associated with membrane structures that have several characteristics of late endosomal compartment. Data indicate that Marburg virus VP40 is able to interact with membranes of the late endosomal compartment independently of other viral proteins (Kolesnikova et al., 2002).(Kolesnikova et al., 2002) pre-GP protein Function: . Two hydrophobic regions have been identified in GP, one at the N-terminus, the other in the C-terminal region. The N-terminal hydrophobic region is not present in the mature protein, indicating that this region serves as a signal peptide. The C-terminal hydrophobic domain is used as a membrane anchor which is adjacent to the short cytoplasmic tail constituted by the last eight amino acids of the protein. Two fatty acid attachment sites were identified at the boundary between membrane anchor and cytoplasmic domain. GP is heavily N- and O-glycosylated containing 19 potential N-linked glycosylation sites and several clusters of hydroxyamino acids which serve as O-linked glycosylation sites (Sanger et al., 2002).(Sanger et al., 2002) VP30 protein Function: . The Marburg virus nucleocapsid complex is composed of four viral proteins (NP, L, VP35, and VP30) and the negative-strand nonsegmented genomic RNA. NP, L, and VP35 are functionally conserved among the order Mononegavirales, whereas VP30, a phosphoprotein, represents a filovirus-specific nucleocapsid protein (Modrof et al., 2001). Phosphorylation of serine residues 40 and 42 is essential for the interaction of the protein with the aggregates of NP, which are built of nucleocapsid-like particles. This interaction is presumed to stand for one step in the maturation of the Marburg virus nucleocapsid (Modrof et al., 2001).(Modrof et al., 2001) VP24 protein Function: . Between the nucleocapsid and the viral envelope, Marburg virus particles contain two proteins, VP24 and the highly abundant VP40, whose function is not yet elucidated (Kolesnikova et al., 2002).(Kolesnikova et al., 2002) L protein Function: Enzyme. Three of the four nucleocapsid proteins, NP, VP35, and L, are sufficient to support replication and transcription of an Marburg virus-specific monocistronic minigenome (Muhlberger et al., 1999). L (encoded by the last gene) is present in nucleocapsids only in catalytic amounts corresponding to its presumed function as RNA-dependent RNA polymerase (Becker and Muhlberger, 1999). As with other negative-strand RNA viruses, the RNA-dependent RNA polymerase of filoviruses is the largest and least abundant viral protein in both the virion and in infected cells (Peters et al., 1996).(Muhlberger et al., 1999)(Becker)(Peters) pre-GP protein Function: . GP is synthesized at the rough endoplasmic reticulum as a precursor of 140 kDa, which carries N-linked sugar side chains from the high mannose type (Sanger et al., 2002).(Sanger et al., 2002) pre-GP protein Function: . GP is transported to the Golgi apparatus where high mannose N-linked sugar side chains are modified to the complex type and, additionally, O-linked carbohydrates are attached (Sanger et al., 2002). New evidence shows that GP is phosphorylated in the Golgi apparatus before the protein reaches the trans-Golgi network (Sanger et al., 2002). As a late step of maturation, GP is cleaved by the prohormone convertase furin in the trans-Golgi network. The precursor, GP0, gives rise to two fragment, GP1 and GP2, which are connected by disulfide linkages (Sanger et al., 2002).(Sanger et al., 2002) GP1 protein Function: . The precursor, GP0, gives rise to two fragments, GP1 and GP2, which are connected by disulfide linkages (Sanger et al., 2002).(Sanger et al., 2002) GP2 protein Function: . The precursor, GP0, gives rise to two fragments, GP1 and GP2, which are connected by disulfide linkages (Sanger et al., 2002). GP2 contains a sequence of several, uncharged hydrophobic amino acids at a distance of 22 (Ebola virus) or 91 (Marburg virus) amino acids from the cleavage site and which bears some structural similarity to the fusion peptides of retroviruses (Feldmann et al., 2001).(Sanger et al., 2002)(Feldmann et al., 2001) GP1/2 protein Function: . A special arrangement of cysteine residues in the GP1/2 molecules allows the formation of an intramolecular disulphide bridge between the two cleavage products. This suggests a stem region consisting of GP1 and GP2 and a crown-like domain on the top formed by GP1 that carries the mass of the carbohydrate side chains. The mature transmembrane glycoprotein is a trimer comprising disulphide-bonded GP1/2 molecules. The mature transmembrane glycoprotein forms spikes without the need for other viral proteins (Feldmann et al., 2001).GP is vectorially transported, mainly to the apical membrane compartment (Sanger et al., 2001).(Feldmann et al., 2001)(Sanger et al., 2002) GP1/2 protein Function: . The mature envelope glycoprotein GP1/2 is anchored in the membrane by a carboxy-terminal hydrophobic domain of GP2. The middle region of GP1/2 is variable, extremely hydrophilic and carries the bulk of N- and O-glycans, which account for more than one-third of the molecular mass of the mature protein. Oligosaccharide side chains differ in their terminal sialylation patterns. Two carboxy-terminal cysteine residues are acylated. GP2 contains a sequence of several uncharged, hydrophobic amino acids at a distance of 22 (Ebola virus) or 91 (Marburg virus) amino acids from the cleavage site and which bears some structural similarity to the fusion peptides of retroviruses. The special arrangement of the cysteine residues in the GP1/2 molecules allows the formation of an intramolecular disulphide bridge between the two cleavage products. This suggests a stem region consisting of GP1 and GP2 and a crown-like domain on the top formed by GP1 that carries the mass of the carbohydrate side chains. It can be assumed that cysteine residue 53 is also critical for maintaining the structure of GP1/2. The mature transmembrane glycoprotein is a trimer comprising disulphide-bonded GP1/2 molecules (Feldmann et al., 2001). The mature form of GP is efficiently transported to the plasma membrane (Becker et al., 1996). GP is vectorially transported, mainly to the apical membrane compartment (Sanger et al., 2001).(Feldmann et al., 2001)(Sanger et al., 2001)(Becker et al., 1996) GP protein Function: . GP is shed from the apical membrane into the medium. Shedding of GP is also detected with Ebola virus, where the protein is found in large quantities in the supernatant of infected cells. The role of shed GP molecules, either soluble or incorporated into virosomes, in the course of Marburg or Ebola hemorrhagic fever is not yet understood (Sanger et al., 2001).(Sanger et al., 2001) Viral capsid Function: . The assembly of new viral particles occurs on the inner surface of the plasma membrane, where VP24 and VP40 apparently associate both with new RNPs and with the cytoplasmic tail of GP2 (Bray and Paragas, 2002).(Bray et al., 2002) Budding virus Function: . Nascent virions become enveloped by the GP-bearing lipid bilayer and exit the cell through budding (Bray and Paragas, 2002). New data demonstrate the compartmentalization of Ebola and Marburg viral proteins in lipid rafts during viral assembly and budding (Bavari et al., 2002).(Bray et al., 2002)(Bavari et al., 2002) Virion Function: . The complete replication cycle takes approximately 12 hours. As for many other viruses, filovirus replication triggers a cascade of reactions in infected cells, including the de novo production of type I interferon (IFN-/), which collectively constitute the innate antiviral response. At the same time, certain viral proteins apparently suppress some of these antiviral mechanisms, giving the virus an advantage over its host. The ability of filoviruses to overcome initial defensive barriers and rapidly disseminate may be an essential factor in their virulence (Bray and Paragas, 2002).(Bray et al., 2002) Furin Function: . Cleavage of GP into GP1 and GP2 was mediated by furin or another subtilisin-like endoprotease with similar substrate specificity (Volchkov et al., 2000).(Volchkov et al., 2000) Furin Function: . Cleavage of GP into GP1 and GP2 was mediated by furin or another subtilisin-like endoprotease with similar substrate specificity (Volchkov et al., 2000).(Volchkov et al., 2000)