Isolation, purification, and amino acid composition of the tunicate hemocyte Thy-1 homolog.
A serologic cross-reacting homolog to rodent Thy-1 glycoproteins has been isolated from hemocyte cell surfaces of the advanced invertebrate group of tunicates. The Thy-1.1 cross-reacting antigenic activity was followed during purification by inhibiting the binding of MRC OX7 monoclonal antibody to pure rat brain Thy-1 in a soluble phase radioimmunoassay. After solubilization in deoxycholate, tunicate hemocyte Thy-1.1 antigenic activity was purified by affinity chromatography using an MRC OX7 monoclonal antibody affinity column, followed by gel filtration. A 602-fold enrichment in the Thy-1.1 antigenic activity, with a yield of 55.6% compared to the starting crude membrane fraction, was obtained. The antigenic activity was associated with a single glycoprotein of molecular size of 3.1 nm and molecular weight estimated at 27,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (15% gels). Amino acid composition of the purified molecule was compared by the S delta Q index of differences in composition to mammalian and non-mammalian Thy-1 glycoproteins, Ig, major histocompatibility complex-encoded polypeptides, beta 2-microglobulin, and other recognition molecules. With this parameter, the tunicate hemocyte Thy-1 homology revealed significant relatedness to avian and mammalian Thy-1 molecules and was interestingly more related to mu chains of primitive vertebrates and to HLA class I and II encoded polypeptides than to Thy-1 molecules of higher vertebrates. Based upon these observations, the tunicate hemocyte Thy-1 homolog seems to represent an ancestral Thy-1 molecule which, in structural terms, may represent an invertebrate member of the Ig superfamily.
Mansour
M H
MH
DeLange
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R
Cooper
E L
EL
D000596:Amino Acids / Q000032:analysis*; D000818:Animals; D000954:Antigens, Surface / Q000302:isolation & purification*; D001923:Brain Chemistry; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D003429:Cross Reactions; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D008970:Molecular Weight; D051381:Rats; D018800:Thy-1 Antigens; D014561:Urochordata / Q000032:analysis*
D000596:Amino Acids; D000954:Antigens, Surface; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D018800:Thy-1 Antigens