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Blast-1 is a human activation-associated glycoprotein expressed on the surface of leukocytes. Analysis of a translated sequence from a Blast-1 cDNA reveals a single hydrophobic sequence which could traverse the plasma membrane, but is devoid of charged residues that might represent a cytoplasmic tail. Consistent with this characteristic, Blast-1 is demonstrated here to be anchored to the cell surface through a glycosyl-phosphatidylinositol (GPI)-containing lipid. Comparison of Blast-1 to other GPI-anchored membrane proteins revealed a striking primary and secondary structure similarity with MRC OX45 and the lymphocyte function antigen LFA-3. The degree of overall amino acid sequence homology reveals that OX45 is a rat homologue of Blast-1. The greatest homology to LFA-3 occurs between their NH2-terminal Ig-like domains. Evidence is presented that demonstrates that Blast-1 and LFA-3 possess a disulfide-bonded second domain. These common characteristics demonstrate a structural and evolutionary relationship between Blast-1, OX45, LFA-3, and CD2, which in turn suggests a functional role for Blast-1 in cell-cell interactions in the immune response. The gene for Blast-1 has been localized to chromosome 1 q21-q23, indistinguishable from the CD1 cluster of Ig superfamily genes, raising the possibility that they may be linked.

Original publication




Journal article


J Exp Med

Publication Date





1087 - 1099


Amino Acid Sequence, Animals, Antigens, CD, Antigens, Surface, CD48 Antigen, CD58 Antigens, Cell Line, Transformed, Chromosome Mapping, Chromosomes, Human, Pair 1, Cricetinae, Glycolipids, Glycosylation, Glycosylphosphatidylinositols, Humans, Lymphocyte Activation, Membrane Glycoproteins, Molecular Sequence Data, Nucleic Acid Hybridization, Phosphatidylinositols, Phytohemagglutinins, Protein Conformation, Sequence Homology, Nucleic Acid, T-Lymphocytes, Type C Phospholipases