Two Epstein-Barr Virus Glycoprotein Complexes
The envelopes of all herpesviruses contain multiple glycoprotein species, each one of which is potentially important to virus entry, to virus egress and to trafficking of virus-producing cells throughout the body. In addition, membrane-associated proteins
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Introduction.
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The gH/gL/gp42 Complex .. Identifying the Components. The Role of the gH/gL/gp42 Complex in Entry into B Lymphocytes. The Role of the gH/gL/gp42 Complex in Entry into Epithelial Cells. Implications for Pathogenesis.
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3 The gN/gM Complex. 3.1 Identifying the Components .. 3.2 The Role of the gN/gM Complex in Virus Exit and Entry.
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Unanswered Questions.
References . .
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1 Introduction The envelopes of all herpesviruses contain multiple glycoprotein species, each one of which is potentially important to virus entry, to virus egress and to trafficking of virus-producing cells throughout the body. In addition, membrane-associated proteins or glycoproteins that are found in the infected cell, but not in the virion, may influence virus assembly and yield. Thus, as a class these molecules have a major impact on virus tropism and virus load and contribute significantly to the outcome of infection. The total complement of membrane proteins encoded by Epstein-Barr virus (EBV) is not yet certain. Currently, eleven unique species are known to be expressed (Table 1), although the information available about several is still quite meager. Least is know about four gene products that have no known homologs in alpha and beta herpesviruses. These are the BDLF3, BILF2, BILF1, and BMRF2 gene products (BAER et al. 1984). The BDLF3 open reading frame (ORF) encodes gp150 (KURILLA et al. 1995; NOLAN and MORGAN 1995), a mucin-like molecule to which N- and O-linked sugars contribute more than 50% of the mass. Recombinant
School of Biological Sciences, University of Missouri-Kansas City, 5007 Rockhill Road, Kansas City, MO 64110, USA
K. Takada (ed.), Epstein-Barr Virus and Human Cancer © Springer-Verlag Berlin Heidelberg 2001
52 Table
L.M. Hutt-Fletcher and C.M. Lake
Open reading frames currently known to express membrane proteins Protein Number of amino acids in Homolog conserved Open reading primary translation product in all known frame herpes viruses gp150 234 None BDLF3 gp78 None 248 BlLF2 gp60 312 None BILFI ?p55 None 356 BMRF2 gp350/220 None BLLFla/b 907/710 gB gp110/125 857 BALF4 gp85 gH 706 BXLF2 gp25 gL 137 BKRF2 gp42 None 223 BZLF2 gp15 gN 102 BLRFI gM 405 gp48/84/113 BBRF3 1.
viruses lacking gpl50 are not impaired for growth in tissue culture (BORZA and HUTT-FLETCHER 1998). The BILF2 ORF encodes gp78 (MACKETT et al. 1990), another highly glycosylated protein that carries primarily N-linked sugars. Both gp 150 and gp78, which are predicted to be type 1 membrane proteins with relatively short cytoplasmic tails, are known to be present in the virion. However, the distribution of the poorly studied products of the BILFI and BMRF2 ORFs remains uncertain. Preliminary data suggest that BILFI encodes a glycosylated protein of approximately 60kDa, which aggregates upon boiling (KENYON and HUTTFLETCHER 1999). This is consistent with its predicted structure as protein that spans the membrane multiple times. The BMRF2 gene product has a similar predicted struct
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