Mutational analysis of the CD6 ligand binding domain.
CD6 belongs to the scavenger receptor cysteine-rich protein superfamily (SRCRSF), which includes a large number of cell surface proteins. The extracellular region of CD6 is composed of three SRCR domains. The membrane proximal SRCR domain of CD6 (CD6D3) specifically binds activated leukocyte cell adhesion molecule (ALCAM), a cell surface protein which is a member of the immunoglobulin superfamily (IgSF). CD6-ligand interactions have been implicated in immune cell adhesion, T cell maturation and the regulation of T cell activation. We tested 13 CD6D3 mutant proteins for binding to ALCAM and a panel of conformationally sensitive anti-CD6D3 monoclonal antibodies (mAbs). CD6D3 residues were classified according to their importance for structural integrity and ligand binding. The results were analyzed in the light of SRCR domain sequence comparison. A number of residues critical for ligand binding or important for structural integrity cluster in the C-terminal region of CD6D3 which is not conserved in other SRCR proteins.
Skonier
J E
JE
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, WA 98121, USA.
Bodian
D L
DL
Emswiler
J
J
Bowen
M A
MA
Aruffo
A
A
Bajorath
J
J
D020410:Activated-Leukocyte Cell Adhesion Molecule; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D015374:Biosensing Techniques; D004252:DNA Mutational Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D051122:Scavenger Receptors, Class B; D017386:Sequence Homology, Amino Acid
D020410:Activated-Leukocyte Cell Adhesion Molecule; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; C062279:CD6 antigen; D006023:Glycoproteins; D008024:Ligands; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D011993:Recombinant Fusion Proteins; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B