alpha Chains, Integrin
The alpha subunits of integrin heterodimers (Integrins), which mediate ligand specificity. There are approximately 18 different alpha chains, exhibiting great sequence diversity; several chains are also spliced into alternative Isoforms. They possess a long extracellular portion (1200 Amino Acids) containing a MIDAS (metal ion-dependent adhesion site) motif, and seven 60-amino acid Tandem Repeats, the last 4 of which form EF Hand Motifs. The intracellular portion is short with the exception of Integrin alpha4.