Karyopherin Alpha 4 (KPNa4)

Karyopherin Alpha 4 shares the sequence similarity with Xenopus importin-alpha and Saccharomyces cerevisiae Srp1. This protein is found to interact with the NLSs of DNA helicase Q1 and SV40 T antigen.

The predicted 521-amino acid QIP1 protein contains the conserved N-terminal binding site for karyopherin-beta and a series of 7 degenerate 'armadillo' repeats, which are 42-amino acid motifs implicated in protein-protein interactions. Human QIP1 has 50% amino acid identity with human KPNA2, 49% with Xenopus importin-alpha, 47% with human KPNA1 , and 46% with S. cerevisiae Srp1. The authors demonstrated that QIP1 interacted with the NLSs of DNA helicase Q1 and SV40 T antigen.