Distinctive Conformation of Minor Site‐Specific Nuclear Localization Signals Bound to Importin‐α

Nuclear localization signals ( NLSs ) contain one or two clusters of basic residues that are recognized by importin‐α. Importin‐α has two NLS ‐binding sites (major and minor), with the major site known as the primary binding site. Using crystallographic and biochemical approaches, we have characterized a group of atypical NLSs that bind primarily to the minor site. Unlike previously characterized NLSs , the C‐terminal residues of these NLSs form an α‐helical turn, which prevents them from binding to the major NLS ‐binding site.