Identification and analysis of a novel heparin-binding glycoprotein encoded by human herpesvirus 7.
Human herpesvirus 6 (HHV-6) and HHV-7 are closely related betaherpesviruses that encode a number of genes with no known counterparts in other herpesviruses. The product of one such gene is the HHV-6 glycoprotein gp82-105, which is a major virion component and a target for neutralizing antibodies. A 1.7-kb cDNA clone from HHV-7 was identified which contains a large open reading frame capable of encoding a predicted primary translational product of 468 amino acids (54 kDa) with 13 cysteine residues and 9 potential N-linked glycosylation sites. This putative protein, which we have termed gp65, was homologous to HHV-6 gp105 (30% identity) and contained a single potential membrane-spanning domain located near its amino terminus. Comparison of the cDNA sequence with that of the viral genome revealed that the gene encoding gp65 contains eight exons, spanning almost 6 kb of the viral genome at the right (3') end of the HHV-7 genome. Northern (RNA) blot analysis with poly(A)(+) RNA from HHV-7-infected cells revealed that the cDNA insert hybridized to a single major RNA species of 1.7 kb. Antiserum raised against a purified, recombinant form of gp65 recognized a protein of roughly 65 kDa in sucrose density gradient-purified HHV-7 preparations; treatment with PNGase F reduced this glycoprotein to a putative precursor of approximately 50 kDa. Gp65-specific antiserum also neutralized the infectivity of HHV-7, while matched preimmune serum did not do so. Finally, analysis of the biochemical properties of recombinant gp65 revealed a specific interaction with heparin and heparan sulfate proteoglycans and not with closely related molecules such as N-acetylheparin and de-N-sulfated heparin. At least two domains of the protein were found to contribute to heparin binding. Taken together, these findings suggest that HHV-7 gp65 may contribute to viral attachment to cell surface proteoglycans.
Skrincosky
D
D
Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA.
Hocknell
P
P
Whetter
L
L
Secchiero
P
P
Chandran
B
B
Dewhurst
S
S
D020816:Amino Acid Motifs; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D006493:Heparin / Q000378:metabolism*; D016199:Herpesvirus 7, Human / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D011233:Precipitin Tests; D012326:RNA Splicing; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D014771:Virion / Q000378:metabolism
D018076:DNA, Complementary; C407562:GP65 protein, Human herpesvirus 7; D006023:Glycoproteins; D011994:Recombinant Proteins; D014759:Viral Envelope Proteins; D006493:Heparin