Epstein-Barr virus genome may encode a protein showing significant amino acid and predicted secondary structure homology with glycoprotein B of herpes simplex virus 1.

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We report significant sequence and predicted secondary structure homology between the herpes simplex virus 1 glycoprotein B (gB) and a protein predicted to be encoded by the BALF4 reading frame of Epstein-Barr virus (EBV). Homology was detectable at the DNA level and was highly significant at the protein level and when evolutionary substitution frequencies of amino acids in related proteins were taken into account. Hydropathic analyses predicted that the two proteins possess conserved N-terminal and C-terminal hydrophobic domains. The N-terminal hydrophobic domains share features in common with known cleavable membrane insertion signal sequences. The amino acid sequences of the C-terminal hydrophobic domains predict three adjacent membrane-spanning segments as had been previously predicted for gB. In an alignment of the two amino acid sequences, 247 of 903 gB residues had a matched pair in the BALF4 sequence, and 247 of 854 BALF4 residues were found to have a matched pair in the gB sequence. In addition, all 10 cysteine residues located outside the predicted signal sequence of both proteins were conserved, as were four predicted N-linked glycosylation sites. In all, 43% of the residues in the aligned sequences are predicted to possess equivalent secondary structures. gB is a virion envelope glycoprotein required for virus entry into cells. The domain of gB determining the rate of entry into cells has been mapped; the predicted structure of this domain in gB and the predicted EBV protein are almost identical. Similarly, the cytoplasmic domain of gB postulated to interact with submembrane proteins was also nearly identical in predicted structure to that of the EBV protein. These results suggest that EBV encodes a protein similar in structure and function to the herpes simplex virus 1 gB.

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