title: Identification and characterization of SRS1, a Toxoplasma gondii surface antigen upstream of and related to SAG1.
abstract: Previous investigations of the major surface antigen (SAG1) promoter of Toxoplasma gondii indicated an ability to function bi-directionally in transient transformation assays at least. This suggests there might be another tachyzoite-specific gene being divergently transcribed from the SAG1 promoter in its normal chromosomal location. To investigate this possibility we have characterized the region upstream of SAG1 and report here a co-directional transcription unit coding for a probable GPI-anchored surface protein with homology to SAG1 and SAG3. This antigen, which had not previously been identified in surface iodination experiments is given the acronym SRS1, for SAG1-related sequence 1. Genomic organization and sequence of a full-length cDNA of SRS1 are presented. Antisera against a recombinant SRS1 protein produced in Escherichia coli, recognize a specific band of 46 kDa in parasite lysates which corresponds to the largest of the GPI-anchored proteins by Western blot. The possible role of this previously unidentified surface antigen is discussed.
authors.affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, CA 94305, USA.
authors.forename: A
authors.initials: A
authors.lastname: Hehl
authors.forename: T
authors.initials: T
authors.lastname: Krieger
authors.forename: J C
authors.initials: JC
authors.lastname: Boothroyd
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D000954:Antigens, Surface / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D008562:Membrane Glycoproteins / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D015800:Protozoan Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D016053:RNA, Protozoan / Q000235:genetics; D011993:Recombinant Fusion Proteins; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014122:Toxoplasma / Q000235:genetics / Q000276:immunology*; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D000954:Antigens, Surface; D018076:DNA, Complementary; D016054:DNA, Protozoan; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D011993:Recombinant Fusion Proteins; C047168:SAG1 antigen, Toxoplasma; C087692:SAG3 protein, Toxoplasma gondii; C109325:SRS1 protein, Toxoplasma gondii