title: A role for tertiary structure in the generation of antigenic diversity and molecular association of the Tams1 polypeptide in Theileria annulata.
abstract: The major merozoite-piroplasm surface antigen (mMPSA) of Theileria annulata, Tams1, is known to be antigenically diverse. The possession of variable N-linked glycosylation sites and removal of monoclonal antibody 5E1 reactivity by mild periodate treatment suggested, previously, that divergent epitopes may be conferred by secondary modification. This study has shown that monoclonal antibody 5E1 and polyspecific antisera raised against the native protein react against divergent amino acid epitopes that are dependent on a molecular conformation that is sensitive to periodate. Therefore, no experimental evidence exists to confirm the sequence prediction that Tams1 undergoes N-linked glycosylation. Data is also presented indicating that the conformation of the antigen results in presentation of divergent regions on the external surface of the molecule, while conserved regions are more likely to be internal and hidden. In addition, non-reducing SDS-PAGE analysis demonstrated that Tams1 can undergo molecular association to form homo-dimers, trimers and multimers. The potential influence of tertiary structure and inter-molecular association on Tams1 diversity and function is discussed.
authors.affiliation: Department of Veterinary Parasitology, Faculty of Veterinary Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Frank
authors.initials: F
authors.lastname: Katzer
authors.forename: Sue
authors.initials: S
authors.lastname: McKellar
authors.forename: Michael A J
authors.initials: MA
authors.lastname: Ferguson
authors.forename: Christine
authors.initials: C
authors.lastname: d'Oliveira
authors.forename: Brian R
authors.initials: BR
authors.lastname: Shiels
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D000940:Antigenic Variation; D000953:Antigens, Protozoan / Q000737:chemistry* / Q000187:drug effects / Q000276:immunology*; D018604:Epitope Mapping; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010504:Periodic Acid / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D013329:Structure-Activity Relationship; D016796:Theileria annulata / Q000737:chemistry* / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D011994:Recombinant Proteins; C113538:Tams1 antigen; D010504:Periodic Acid; C009288:metaperiodate