A cytotoxic ribonuclease variant with a discontinuous nuclear localization signal constituted by basic residues scattered over three areas of the molecule.
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 alpha/beta 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 alpha 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.
Rodríguez
M
M
Laboratori d'Enginyeria de Proteïnes, Departament de Biologia, Facultat de Ciències, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain.
Benito
A
A
Tubert
P
P
Castro
J
J
Ribó
M
M
Beaumelle
B
B
Vilanova
M
M
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D024361:Amino Acids, Basic / Q000737:chemistry*; D016923:Cell Death; D002467:Cell Nucleus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D019913:Nuclear Localization Signals / Q000737:chemistry*; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012259:Ribonuclease, Pancreatic / Q000737:chemistry / Q000378:metabolism*; D051901:Smad4 Protein / Q000378:metabolism; D014407:Tumor Cells, Cultured; D028901:alpha Karyopherins / Q000378:metabolism
D024361:Amino Acids, Basic; D019913:Nuclear Localization Signals; D051901:Smad4 Protein; D028901:alpha Karyopherins; D012259:Ribonuclease, Pancreatic