title: Epitopes of adhesion-perturbing monoclonal antibodies map within a predicted alpha-helical domain of the integrin beta 1 subunit.
abstract: Several recent studies have demonstrated the involvement of various domains of the beta 1 integrin subunit in ligand binding. Thus, specific amino acids have been shown to be important in divalent cation binding, and others have been implicated by peptide crosslinking to play an intimate role in integrin-ligand interactions. Added to these data are previous observations that a group of adhesion-blocking anti-chicken beta 1 antibodies mapped within the first 160 amino acid residues of the subunit. These observations suggested that this region plays a critical role in integrin ligand recognition. In order to further define the domain in which the epitopes for these antibodies are clustered, a series of mouse/chicken chimeric beta 1 constructs were examined for their reactivity with each of these antibodies. Most of the antibodies recognize a region between residues 124 to 160 of the chicken beta 1 subunit. Computer modeling predicted a possible amphipathic alpha-helical configuration for the region between residues 141 to 160. Consistent with this prediction, circular dichroism and NMR analysis revealed a tendency for a synthetic peptide containing these residues to form an alpha-helix. The significance of this structural characteristic was demonstrated by a mutation at residue 149 that disrupted the alpha-helix formation and resulted in a loss of the ability to form heterodimers with alpha subunits, localize to focal contacts, or be transported to the cell surface. The direct involvement of residues 141 to 160 in ligand binding was supported by the ability of a peptide with this sequence to elute integrins from a fibronectin affinity column. Thus, our data suggest that residues 141 to 160 of the integrin beta 1 subunit, when arranged in an alpha-helix configuration, participate in ligand binding.
authors.affiliation: Wistar Institute, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Shih
authors.forename: D
authors.initials: D
authors.lastname: Boettiger
authors.forename: C A
authors.initials: CA
authors.lastname: Buck
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002448:Cell Adhesion; D002645:Chickens; D002942:Circular Dichroism; D018604:Epitope Mapping; D018985:Epitopes, B-Lymphocyte / Q000276:immunology / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D005807:Genes, Overlapping; D019012:Integrin beta1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000911:Antibodies, Monoclonal; D018985:Epitopes, B-Lymphocyte; D005353:Fibronectins; D019012:Integrin beta1; D010455:Peptides; D011993:Recombinant Fusion Proteins