Integrin LFA-1 alpha subunit contains an ICAM-1 binding site in domains V and VI.
In order to identify a binding site for ligand intercellular adhesion molecule-1 (ICAM-1) on the beta 2 integrin lymphocyte function-associated antigen-1 (LFA-1), protein fragments of LFA-1 were made by in vitro translation of a series of constructs which featured domain-sized deletions starting from the N-terminus of the alpha subunit of LFA-1. Monoclonal antibodies and ICAM-1 were tested for their ability to bind to these protein fragments. Results show that the putative divalent cation binding domains V and VI contain an ICAM-1 binding site. A series of consecutive peptides covering these domains indicated two discontinuous areas as specific contact sites: residues 458-467 in domain V and residues 497-516 in domain VI. A three-dimensional model of these domains of LFA-1 was constructed based on the sequence similarity to known EF hands. The two regions critical for the interaction of LFA-1 with ICAM-1 lie adjacent to each other, the first next to the non-functional EF hand in domain V and the second coinciding with the potential divalent cation binding loop in domain VI. The binding of ICAM-1 with the domain V and VI region in solution was not sensitive to divalent cation chelation. In short, a critical motif for ICAM-1 binding to the alpha subunit of LFA-1 is shared between two regions of domains V and VI.
Stanley
P
P
Leukocyte Adhesion Laboratory, Imperial Cancer Research Fund, London, UK.
Bates
P A
PA
Harvey
J
J
Bennett
R I
RI
Hogg
N
N
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002413:Cations, Divalent / Q000494:pharmacology; D015815:Cell Adhesion Molecules / Q000276:immunology / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004305:Dose-Response Relationship, Drug; D006801:Humans; D018799:Intercellular Adhesion Molecule-1; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000378:metabolism
D000911:Antibodies, Monoclonal; D002413:Cations, Divalent; D015815:Cell Adhesion Molecules; D016169:Lymphocyte Function-Associated Antigen-1; D010446:Peptide Fragments; D018799:Intercellular Adhesion Molecule-1