Biochemical analysis of two cell surface glycoprotein complexes, very common antigen 1 and very common antigen 2. Relationship to very late activation T cell antigens

Abstract

Two mouse monoclonal antibodies (mAb), AJ2 and J143, define two related human cell surface protein complexes, very common antigen 1 (VCA-1) and very common antigen 2 (VCA-2). In the present report, these complexes have been defined with respect to: (i) subunit arrangement; (ii) monoclonal antibody binding sites; (iii) carbohydrate content; (iv) homology to other cell surface protein complexes; and (v) possible functional roles. Analysis of the antigens from a human melanoma cell line, MeWo, reveals that VCA-1 is a noncovalently linked heterodimer of 170- and 140 (designated 1401)-kDa polypeptides. mAb AJ2 reacts with an epitope on the 1401-kDa polypeptide. VCA-2 is composed of the same 1401-kDa polypeptide as VCA-1 and another 170-kDa species; this 170-kDa species consists of a second distinct 140-kDa (designated 140(2)) and a 30-kDa polypeptide which are disulfide-bonded. Indirect evidence indicates that mAb J143 reacts with an epitope on this 170-kDa complex. Peptide mapping has shown that the complexes are members of a family of cell surface proteins that include antigens present on activated T cells (designated very late activation antigens). Since VCA-2 is found predominantly on the basal membrane of adherent cells and its expression increases 12-fold when HUT-102 lymphoblastoid cells are grown as an adherent cell culture, we suggest that VCA-2 plays a role in cellular adherence.