Blast-1 possesses a glycosyl-phosphatidylinositol (GPI) membrane anchor, is related to LFA-3 and OX-45, and maps to chromosome 1q21-23.
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.
Staunton
D E
DE
Department of Pathology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Fisher
R C
RC
LeBeau
M M
MM
Lawrence
J B
JB
Barton
D E
DE
Francke
U
U
Dustin
M
M
Thorley-Lawson
D A
DA
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D000954:Antigens, Surface; D000071178:CD48 Antigen; D018968:CD58 Antigens; D002461:Cell Line, Transformed; D002874:Chromosome Mapping; D002878:Chromosomes, Human, Pair 1; D006224:Cricetinae; D006017:Glycolipids / Q000032:analysis*; D006031:Glycosylation; D017261:Glycosylphosphatidylinositols; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010716:Phosphatidylinositols / Q000032:analysis* / Q000378:metabolism; D010835:Phytohemagglutinins / Q000494:pharmacology; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid; D013601:T-Lymphocytes / Q000032:analysis; D010738:Type C Phospholipases / Q000378:metabolism
D015703:Antigens, CD; D000954:Antigens, Surface; D000071178:CD48 Antigen; C000604065:CD48 protein, human; D018968:CD58 Antigens; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins; D010716:Phosphatidylinositols; D010835:Phytohemagglutinins; D010738:Type C Phospholipases