Use of Lectins for Characterization of O-Linked Glycans of Herpes Simplex Virus Glycoproteins

The existence of O -linked glycans in viral glycoproteins was described in the early 1980s for enveloped viruses such as herpes simplex virus type 1 (HSV-1), vaccinia virus, and mouse hepatitis virus (1 -4 ). Glycoprotein C of HSV-1 (designated gC-1) was demonstrated to contain domains, in which numerous O -linked glycans were concentrated to pronase-resistant clusters (5 -7 ), thereby resembling the organization of mucins (8 ). Thus glycoprotein, containing nine sites for N -linked glycosylation in addition to the O -linked glycans, is responsible for several important biological activities, including virus receptor binding (9 ) and binding of factor C3b of the complement system (10 ). The function of the O -linked glycans in these activities remains unclear, but it is conceivable that their clustered appearance may cause gC-1 to adopt an extended fibrous conformation (11 ), as originally demonstrated for the O -linked glycans of mucins (8 ). Use of lectins facilitates a structural analysis of clustered O -linked glycans of gC-1 and it is possible that the methodology presented here may be of more general use, as similar arrangements of clustered O -linked glycans are present in an increasing number known glycoproteins of other enveloped viruses including herpes simplex virus type 2 (12 ,13 ), Epstein-Barr virus (14 ), and respiratory syncytial virus (15 ).