Transportin 2 (TNPO2)

Transportin-1 (KPNB2) interacts directly and specifically with M9, the bidirectional transport signal of the nuclear shuttling protein hnRNPA1 and mediates hnRNPA1 nuclear import. In the course of isolating additional transportin-1 cDNAs, Siomi et al. (1997) isolated cDNAs encoding a related protein that they designated 'transportin-2.' The sequence of the predicted 894-amino acid protein shares 84% identity with that of transportin-1. One notable difference is that transportin-2 contains a short extra sequence within the region corresponding to the M9-interacting domain of transportin-1. Far Western blotting showed that transportin-2 and transportin-1 have different substrate specificities. Siomi et al. (1997) suggested that the insert in transportin-2 modifies its interaction with import substrates.