文摘
Nuclear import of proteins is determined by specific signals that allow them to bind to receptors that mediate their energy-dependent transport through the nuclear pore. These signals are termed nuclear localization signals and do not constitute a specific consensus sequence. Among them, the most characterized correspond to monopartite and bipartite nuclear localization signals, which interact with the importin α/β heterodimer. We previously described a cytotoxic variant of human pancreatic-ribonuclease that is actively transported into the nucleus. Here, we show that this protein interacts with importin α through different basic residues, including Lys1 and the arginine clusters 31–33 and 89–91. Although these residues are scattered along the sequence, they are close in the three-dimensional structure of the protein and their topological disposition strongly resembles that of a classical bipartite nuclear localization signal.