An abundant chick gizzard integrin is the avian alpha 1 beta 1 integrin heterodimer and functions as a divalent cation-dependent collagen IV receptor.

The alpha-subunit of an abundant chick gizzard integrin was isolated (T. Kelly, L. Molony, and K. Burridge, 1987, J. Biol. Chem. 262, 17,189-17,199) and fragmented by proteolytic digestion. The N-terminal sequences of the intact polypeptide and of several internal peptides were determined and were found to be highly homologous to the mammalian integrin alpha 1-subunit. Monoclonal antibodies to the chick integrin beta 1-chain react on immunoblots with the gizzard integrin beta-subunit (U. Hofer, J. Syfrig, and R. Chiquet-Ehrismann, 1990, J. Biol. Chem. 265, 14,561-14,565). The chain composition of the abundant chick gizzard integrin is therefore alpha 1 beta 1. Polyclonal antibodies to the avian integrin alpha 1-subunit block attachment of embryonic gizzard cells to human and chick collagen IV completely and inhibit attachment to mouse Engelbreth-Holm-Swarm (EHS) tumor laminin partially. In ELISA-style receptor assays, the isolated alpha 1 beta 1 integrin bound to human and chick collagen IV and to mouse EHS tumor and chick heart laminin. While the binding to collagen IV was abolished by removal of divalent cations, the binding to laminin was not sensitive to EDTA under the conditions used. Collagen I bound the isolated avian alpha 1 beta 1 integrin only weakly. As collagen IV was the only extracellular matrix protein for which a consistent, divalent cation-dependent, binding to the avian alpha 1 beta 1 integrin could be demonstrated in both cellular and molecular assays we suggest that it is a preferred ligand for this integrin.