title: Disorder in the nuclear pore complex: the FG repeat regions of nucleoporins are natively unfolded.
abstract: Nuclear transport proceeds through nuclear pore complexes (NPCs) that are embedded in the nuclear envelope of eukaryotic cells. The Saccharomyces cerevisiae NPC is comprised of 30 nucleoporins (Nups), 13 of which contain phenylalanine-glycine repeats (FG Nups) that bind karyopherins and facilitate the transport of karyopherin-cargo complexes. Here, we characterize the structural properties of S. cerevisiae FG Nups by using biophysical methods and predictive amino acid sequence analyses. We find that FG Nups, particularly the large FG repeat regions, exhibit structural characteristics typical of "natively unfolded" proteins (highly flexible proteins that lack ordered secondary structure). Furthermore, we use protease sensitivity assays to demonstrate that most FG Nups are disordered in situ within the NPCs of purified yeast nuclei. The conclusion that FG Nups constitute a family of natively unfolded proteins supports the hypothesis that the FG repeat regions of Nups form a meshwork of random coils at the NPC through which nuclear transport proceeds.
authors.affiliation: Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Denning
authors.forename: Samir S
authors.initials: SS
authors.lastname: Patel
authors.forename: Vladimir
authors.initials: V
authors.lastname: Uversky
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Fink
authors.forename: Michael
authors.initials: M
authors.lastname: Rexach
mesh_terms: D021581:Active Transport, Cell Nucleus; D000596:Amino Acids / Q000737:chemistry; D055592:Biophysical Phenomena; D001703:Biophysics; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D002850:Chromatography, Gel; D002942:Circular Dichroism; D019286:Endopeptidase K / Q000494:pharmacology; D010450:Endopeptidases / Q000737:chemistry; D005998:Glycine / Q000737:chemistry; D022022:Nuclear Pore / Q000473:pathology*; D010649:Phenylalanine / Q000737:chemistry; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D013395:Sucrose / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000596:Amino Acids; D011994:Recombinant Proteins; D010649:Phenylalanine; D013395:Sucrose; D010450:Endopeptidases; D019286:Endopeptidase K; D005998:Glycine