 The major NLS binding site is found towards the N-terminus, with a minor site being found at the C-terminus.As well as the ARM structures, Importin-α also contains a 90 amino acid N-terminal region, responsible for binding to Importin-β, known as IBB (Importin-β binding domain).This is also a site of autoinhibition, and is implicated in the release of cargo once importin-α reaches the nucleus.