Protein of the integrin family of cell surface heterodimeric receptors that mediates dynamic cell-to-cell as well as cell-to-matrix adhesion. Integrins function as mechanochemical sensors and transducers able to change rapidly and reversibly their adhesive functions by modulating their ligand-binding affinity. Each subunit has a large N-terminal extracellular domain followed by a transmembrane domain and a short C-terminal cytoplasmic region. Some subclasses of integrins share a common beta chain while having different alpha chains.