Determinants of ligand binding specificity of the alpha(1)beta(1) and alpha(2)beta(1) integrins.

Dickeson SK, Mathis NL, Rahman M, Bergelson JM, Santoro SA
J Biol Chem. 1999 274 (45): 32182-91

PMID: 10542255 · DOI:10.1074/jbc.274.45.32182

The alpha(1)beta(1) and alpha(2)beta(1) integrins are cell surface collagen receptors. Cells expressing the alpha(1)beta(1) integrin preferentially adhere to collagen IV, whereas cells expressing the alpha(2)beta(1) integrin preferentially adhere to collagen I. Recombinant alpha(1) and alpha(2) integrin I domains exhibit the same collagen type preferences as the intact integrins. In addition, the alpha(2) integrin I domain binds echovirus 1; the alpha(1) I domain does not. To identify the structural components of the I domains responsible for the varying ligand specificities, we have engineered several alpha(1)/alpha(2) integrin I domain chimeras and evaluated their virus and collagen binding activities. Initially, large secondary structural components of the alpha(2) I domain were replaced with corresponding regions of the alpha(1) I domain. Following analysis in echovirus 1 and collagen binding assays, chimeras with successively smaller regions of alpha(1) I were constructed and analyzed. The chimeras were analyzed by ELISA with several different alpha(2) integrin monoclonal antibodies to assess their proper folding. Three different regions of the alpha(1) I domain, when present in the alpha(2) I domain, conferred enhanced collagen IV binding activity upon the alpha(2) I domain. These include the alpha3 and alpha5 helices and a portion of the alpha6 helix. Echovirus 1 binding was lost in a chimera containing the alphaC-alpha6 loop; higher resolution mapping identified Asn(289) as playing a critical role in echovirus 1 binding. Asn(289) had not been implicated in previous echovirus 1 binding studies. Taken together, these data reveal the existence of multiple determinants of ligand binding specificities within the alpha(1) and alpha(2) integrin I domains.

MeSH Terms (16)

Amino Acid Sequence Binding Sites Cloning, Molecular Collagen Enzyme-Linked Immunosorbent Assay Escherichia coli Humans Integrin alpha1beta1 Integrin beta1 Integrins Ligands Models, Molecular Molecular Sequence Data Protein Conformation Receptors, Collagen Structure-Activity Relationship

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