Biochemical characterization of VLA-1 and VLA-2. Cell surface heterodimers on activated T cells.
The very late antigen complexes VLA-1 and VLA-2 which appear on long-term activated human T cells have been characterized with respect to 1) subunit arrangement, 2) location of monoclonal antibody (MAb) binding sites, 3) carbohydrate content, and 4) protein homology. Cross-linking experiments showed that the VLA-1 complex is a heterodimer composed of an Mr 210,000 subunit (alpha 1) in acid-labile association with an Mr 130,000 subunit (beta). The VLA-2 complex is a heterodimer with an Mr 165,000 subunit (alpha 2) in base-labile association with the Mr 130,000 beta subunit. The subunits of VLA-1 (alpha 1 beta) and VLA-2 (alpha 2 beta) each appear to be arranged with 1:1 stoichiometry. The MAb A-1A5 has been shown to bind to an epitope on the common beta subunit, consistent with its recognition of both the VLA-1 and VLA-2 heterodimers. On the other hand, MAb TS2/7 bound to an epitope of the alpha 1 subunit, thus explaining the specific recognition of the VLA-1 heterodimer by TS2/7. Digestion of the alpha 1, alpha 2, and beta subunits with neuraminidase and with endoglycosidase F revealed that each subunit contains substantial sialic acid and N-linked carbohydrate. By one-dimensional peptide mapping, the alpha 1, alpha 2, and beta subunits were shown to be highly nonhomologous with respect to each other, although each subunit from different T cell sources appeared highly homologous if not identical.
Hemler
M E
ME
Jacobson
J G
JG
Strominger
J L
JL
D000911:Antibodies, Monoclonal / Q000032:analysis*; D001665:Binding Sites; D002241:Carbohydrates / Q000032:analysis; D010450:Endopeptidases / Q000378:metabolism; D000939:Epitopes / Q000032:analysis; D006026:Glycoside Hydrolases / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008970:Molecular Weight; D012697:Serine Endopeptidases; D013601:T-Lymphocytes / Q000032:analysis*
D000911:Antibodies, Monoclonal; D002241:Carbohydrates; D000939:Epitopes; D046911:Macromolecular Substances; D006026:Glycoside Hydrolases; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D010450:Endopeptidases; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase