TY - JOUR
T1 - The N-glycan structures of the antigenic variants of chlorovirus PBCV-1 major capsid protein help to identify the virus-encoded glycosyltransferases
AU - Speciale, Immacolata
AU - Duncan, Garry A.
AU - Unione, Luca
AU - Agarkova, Irina V.
AU - Garozzo, Domenico
AU - Jimenez-Barbero, Jesus
AU - Lin, Sicheng
AU - Lowary, Todd L.
AU - Molinaro, Antonio
AU - Noel, Eric
AU - Laugieri, Maria Elena
AU - Tonetti, Michela G.
AU - Van Etten, James L.
AU - De Castro, Cristina
N1 - Publisher Copyright:
© 2019 Speciale et al.
PY - 2019/4/5
Y1 - 2019/4/5
N2 - The chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1) is a large dsDNA virus that infects the microalga Chlorella variabilis NC64A. Unlike most other viruses, PBCV-1 encodes most, if not all, of the machinery required to glycosylate its major capsid protein (MCP). The structures of the four N-linked glycans from the PBCV-1 MCP consist of nonasaccharides, and similar glycans are not found elsewhere in the three domains of life. Here, we identified the roles of three virus-encoded glycosyltransferases (GTs) that have four distinct GT activities in glycan synthesis. Two of the three GTs were previously annotated as GTs, but the third GT was identified in this study. We determined the GT functions by comparing the WT glycan structures from PBCV-1 with those from a set of PBCV-1 spontaneous GT gene mutants resulting in antigenic variants having truncated glycan structures. According to our working model, the virus gene a064r encodes a GT with three domains: domain 1 has α-L-rhamnosyltransferase activity, domain 2 has an β-L-rhamnosyltransferase activity, and domain 3 is a methyltransferase that decorates two positions in the terminal β-L-rhamnose (Rha) unit. The a075l gene encodes α-xylosyltransferase that attaches the distal D-xylose (Xyl) unit to the L-fucose (Fuc) that is part of the conserved N-glycan core region. Last, gene a071r encodes a GT that is involved in the attachment of a semiconserved element, β-D-Rha, to the same L-Fuc in the core region. Our results uncover GT activities that assemble four of the nine residues of the PBCV-1 MCP N-glycans.
AB - The chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1) is a large dsDNA virus that infects the microalga Chlorella variabilis NC64A. Unlike most other viruses, PBCV-1 encodes most, if not all, of the machinery required to glycosylate its major capsid protein (MCP). The structures of the four N-linked glycans from the PBCV-1 MCP consist of nonasaccharides, and similar glycans are not found elsewhere in the three domains of life. Here, we identified the roles of three virus-encoded glycosyltransferases (GTs) that have four distinct GT activities in glycan synthesis. Two of the three GTs were previously annotated as GTs, but the third GT was identified in this study. We determined the GT functions by comparing the WT glycan structures from PBCV-1 with those from a set of PBCV-1 spontaneous GT gene mutants resulting in antigenic variants having truncated glycan structures. According to our working model, the virus gene a064r encodes a GT with three domains: domain 1 has α-L-rhamnosyltransferase activity, domain 2 has an β-L-rhamnosyltransferase activity, and domain 3 is a methyltransferase that decorates two positions in the terminal β-L-rhamnose (Rha) unit. The a075l gene encodes α-xylosyltransferase that attaches the distal D-xylose (Xyl) unit to the L-fucose (Fuc) that is part of the conserved N-glycan core region. Last, gene a071r encodes a GT that is involved in the attachment of a semiconserved element, β-D-Rha, to the same L-Fuc in the core region. Our results uncover GT activities that assemble four of the nine residues of the PBCV-1 MCP N-glycans.
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U2 - 10.1074/jbc.RA118.007182
DO - 10.1074/jbc.RA118.007182
M3 - Article
C2 - 30737276
AN - SCOPUS:85064405942
SN - 0021-9258
VL - 294
SP - 5688
EP - 5699
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 14
ER -