Functions as a component of the nuclear pore complex (NPC). NPC components, collectively referred to as nucleoporins (NUPs), can play the role of both NPC structural components and of docking or interaction partners for transiently associated nuclear transport factors. Active directional transport is assured by both, a Phe-Gly (FG) repeat affinity gradient for these transport factors across the NPC and a transport cofactor concentration gradient across the nuclear envelope. Involved in nuclear protein import. Required for efficient nuclera import of both an SV40 nuclear localization signal-containing reporter protein and the pap1 component of the stress response MAP kinase pathway. Required for proper mitotic progression. Interacts with pap1. Nucleus; nucleolus; nuclear rim. Belongs to the importin alpha family.