title: The Saccharomyces cerevisiae nucleoporin Nup2p is a natively unfolded protein.
abstract: 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 A) 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.
authors.affiliation: Department of Biological Sciences, Stanford University, Stanford, California 94305, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Denning
authors.forename: Vladimir
authors.initials: V
authors.lastname: Uversky
authors.forename: Samir S
authors.initials: SS
authors.lastname: Patel
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Fink
authors.forename: Michael
authors.initials: M
authors.lastname: Rexach
mesh_terms: D015153:Blotting, Western; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003593:Cytoplasm / Q000378:metabolism; D019286:Endopeptidase K / Q000494:pharmacology; D006358:Hot Temperature; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D021381:Protein Transport; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D013395:Sucrose / Q000494:pharmacology; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: C400753:NUP2 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D013395:Sucrose; D019286:Endopeptidase K