THE CD58 (LFA-3) BINDING-SITE IS A LOCALIZED AND HIGHLY-CHARGED SURFACE-AREA ON THE AGFCC'C'' FACE OF THE HUMAN CD2 ADHESION DOMAIN

Using site-directed mutagenesis in conjunction with NMR structural dat a on the adhesion domain of human CD2, we have defined the binding reg ion for CD58. Previous structural studies of rat and human CD2 indicat e that this adhesion domain is immunoglobulin-like. Here we report tha t the CD58 binding site is a well-circumscribed, charged surface area covering almost-equal-to 770 angstrom2 on the AGFCC'C'' face of the CD 2 beta barrel. This site contains beta-strand residues in the carboxyl -terminal half of the F strand (including Lys-82 and Tyr-86), the top of the C strand (Asp-32 and Lys-34), and the C' strand (Gln-46), which are all solvent exposed. In addition, several exposed residues on the FG loop (Gly-90, Lys-91, Asn-92, and Val-93), the CC' loop (Lys-41 an d Lys-43), and the C'C'' loop (Arg-48 and Lys-51) form this site. In c ontrast, neither residues on the more peripheral G and C'' strands of the same CD2 surface nor residues on B, E, and D strands of the opposi te face are involved in CD58 binding. This CD58 binding site is predic ted to lie most distal to the T-lymphocyte surface membrane, with read y access to CD58 on the surface of the opposing antigen-presenting cel l.