Structural basis of recognition of monopartite and bipartite nuclear localization sequences by mammalian importin-α11Edited by K. Nagai

• DOI: 10.1006/jmbi.2000.3642
• Publication Date: 2002-09-18T19:24:54Z
• Authors: Marcos R.M. Fontes; Trazel Teh; Bostjan Kobe
• Keywords: Models, Molecular; Biochemistry & Molecular Biology; Kinase; 570; Location; Karyopherin-alpha; Molecular Sequence Data; Nuclear Localization Signals; Transport; Importin-alpha/karyopherin-alpha; Karyopherins; Crystallography, X-Ray; Protein Structure, Secondary; Protein Import; Mice; Structure-Activity Relationship; 03 medical and health sciences; Large-t-antigen; Animals; Nucleoplasmin Nls; Amino Acid Sequence; Nucleoplasmins; Conserved Sequence; Signal; 0303 health sciences; Simian Virus 40 (sv40) Large T-antigen Nls; Binding Sites; Nuclear Proteins; Requirements; Binding; Phosphoproteins; Peptide Fragments; Protein Structure, Tertiary; Recognition; Mutagenesis; Mutation; Nuclear Localization Sequence (nls); X-ray Crystal Structure; Oligopeptides; Protein Binding

Importin-alpha is the nuclear import receptor that recognizes cargo proteins which contain classical monopartite and bipartite nuclear localization sequences (NLSs), and facilitates their transport into the nucleus. To determine the structural basis of the recognition of the two classes of NLSs by mammalian importin-alpha, we co-crystallized an N-terminally truncated mouse receptor protein with peptides corresponding to the monopartite NLS from the simian virus 40 (SV40) large T-antigen, and the bipartite NLS from nucleoplasmin. We show that the monopartite SV40 large T-antigen NLS binds to two binding sites on the receptor, similar to what was observed in yeast importin-alpha. The nucleoplasmin NLS-importin-alpha complex shows, for the first time, the mode of binding of bipartite NLSs to the receptor. The two basic clusters in the NLS occupy the two binding sites used by the monopartite NLS, while the sequence linking the two basic clusters is poorly ordered, consistent with its tolerance to mutations. The structures explain the structural basis for binding of diverse NLSs to the sole receptor protein.