Import of proteins with classical NLS composed of one or two clusters of basic residues is initiated by binding to the importin alpha/beta heterodimer, where importin alpha acts as an adapter subunit to bridge NLS cargos to importin beta, which transports the whole complex through the nuclear envelope (By similarity). Involved in the nuclear accumulation of the light-dependent developmental regulator velA (PubMed:20543063). Forms a complex with an importin beta subunit (By similarity). Interacts with velA (PubMed:20543063). Belongs to the importin alpha family.