The Saccharomyces cerevisiae Nucleoporin Nup2p Is a Natively Unfolded Protein

• Published in: The Journal of biological chemistry 2002-09, Vol.277 (36), p.33447-33455
• Main Authors: Denning, Daniel P., Uversky, Vladimir, Patel, Samir S., Fink, Anthony L., Rexach, Michael
• Format: Article
• Language: English
• Subjects: Blotting, Western; Centrifugation, Density Gradient; Chromatography, Gel; Circular Dichroism; Cytoplasm - metabolism; Endopeptidase K - pharmacology; Hot Temperature; Nuclear Pore Complex Proteins - metabolism; Protein Conformation; Protein Folding; Protein Structure, Secondary; Protein Transport; Recombinant Proteins - metabolism; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - metabolism; Spectroscopy, Fourier Transform Infrared; Sucrose - pharmacology; Time Factors; Ultraviolet Rays
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M203499200

Little is known about the structure of the individual nucleoporins that form eukaryotic nuclear pore complexes (NPCs). We report here in vitro physical and structural characterizations of a full-length nucleoporin, the Saccharomyces cerevisiae protein Nup2p. Analyses of the Nup2p structure by far-UV circular dichroism (CD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, protease sensitivity, gel filtration, and sedimentation velocity experiments indicate that Nup2p is a “natively unfolded protein,” belonging to a class of proteins that exhibit little secondary structure, high flexibility, and low compactness. Nup2p possesses a very large Stokes radius (79 Å) in gel filtration columns, sediments slowly in sucrose gradients as a 2.9 S particle, and is highly sensitive to proteolytic digestion by proteinase K; these characteristics suggest a structure of low compactness and high flexibility. Spectral analyses (CD and FTIR spectroscopy) provide additional evidence that Nup2p contains extensive regions of structural disorder with comparatively small contributions of ordered secondary structure. We address the possible significance of natively unfolded nucleoporins in the mechanics of nucleocytoplasmic trafficking across NPCs.