Integrins (IG) are receptors which mediate the attachment between cells or to extracellular matrix. They are involved in cellular signaling and cell cycle. IGs contain α and β chain. IG subunits span the cell membrane. Both subunits bind divalent cations some of which bind the ligands which interact with IG. Some IGs contain an insertion domain named I domain. For more details see Molecular Playground/IntegrinBeta1.