Mutations in and near the second calcium-binding domain of integrin alphaIIb affect the structure and function of integrin alphaIIbbeta3. Biochem J 2004 Apr 15;379(Pt 2):449-59
Date
12/13/2003Pubmed ID
14670082Pubmed Central ID
PMC1224065DOI
10.1042/BJ20030615Scopus ID
2-s2.0-2342526544 (requires institutional sign-in at Scopus site) 5 CitationsAbstract
Calcium-binding domains in the alpha-subunit of integrins contain a central loop structure. To examine the importance of the loop structure, a series of alphaIIb mutants containing changes to the calcium-liganding amino acids have been constructed. Significantly, none of the mutant alphaIIbbeta3 complexes was detected on the surface of transfected cells, but mutant pro-alphaIIb was detected in cell lysates in complex with beta3. To study the importance of the regions flanking the second calcium-binding domain for ligand-binding and ligand-binding specificity, three alphaIIb/alpha5 chimaeras containing alpha5 sequences flanking or flanking and including the second calcium-binding domain were constructed. The chimaera containing both alpha5-flanking regions was not expressed on the cell surface, but FR1 and FR2, substituting either the first or second flanking region, were expressed. FR1beta3-transfected cells lost the ability to adhere to fibrinogen and to support aggregation and had minimal fibrinogen-binding ability. The heterodimer complex was less stable than the wild-type. FR2beta3-transfected cells adhered to fibrinogen and bound soluble fibrinogen with higher affinity when compared with wild-type. In addition, the heterodimer complex was more stable than wild-type. These results indicate that the conformation of the second calcium-binding domain is critical for maturation of the alphaIIbbeta3 complex and expression on the cell surface and that the surrounding sequences are critical for alphaIIbbeta3 function.
Author List
Gidwitz S, Temple B, White GC 2ndAuthor
Gilbert C. White MD Professor in the Medicine department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsBinding Sites
Calcium
Cell Adhesion
Cell Line
Cricetinae
Ligands
Models, Molecular
Platelet Glycoprotein GPIIb-IIIa Complex
Platelet Membrane Glycoprotein IIb
Point Mutation
Protein Structure, Tertiary
Recombinant Fusion Proteins
