CHICK INTEGRIN-ALPHA-V SUBUNIT MOLECULAR ANALYSIS REVEALS HIGH CONSERVATION OF STRUCTURAL DOMAINS AND ASSOCIATION WITH MULTIPLE BETA-SUBUNITS IN EMBRYO FIBROBLASTS

We have cloned and characterized a chick homologue of the human vitronectin receptor α subunit (αv) whose primary sequence is 83% identical with its human counterpart but less than 40% identical with any other known integrin α subunit. Comparison of the chick and human sequences reveals several highly conserved regions, including the cytoplasmic domain. The putative ligand binding domain contains αv-specific residues that may contribute to ligand binding specificity. These are concentrated in three regions that are located before and between the first three Ca2+ binding domains. Polyclonal antibodies raised against two peptides deduced from the putative cytoplasmic and extracellular domains of the chick αv sequence recognize specifically integrin heterodimers in chick embryo fibroblasts. At least three putative β subunits coimmunoprecipitate with the chick αv subunit. In addition to a protein with the same molecular weight as β3 (94K), protein bands of Mr 84K and 110K are also coprecipitated. By successive immunodepletions, we demonstrate that this latter Mr 110K subunit is β1, which appears to be one of the αv-associated subunits in chick embryo fibroblasts. © 1990, American Chemical Society. All rights reserved.