Plasticity of an Ultrafast Interaction between Nucleoporins and Nuclear Transport Receptors

• Published in: Cell Vol. 163; no. 3; pp. 734 - 745
• Main Authors: Milles, Sigrid, Mercadante, Davide, Aramburu, Iker Valle, Jensen, Malene Ringkjøbing, Banterle, Niccolò, Koehler, Christine, Tyagi, Swati, Clarke, Jane, Shammas, Sarah L., Blackledge, Martin, Gräter, Frauke, Lemke, Edward A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 22.10.2015; Elsevier; Cell Press
• Subjects: Active Transport, Cell Nucleus; Biochemistry, Molecular Biology; Crystallography, X-Ray; Fluorescence Resonance Energy Transfer; Humans; Karyopherins - chemistry; Karyopherins - metabolism; Life Sciences; Models, Molecular; Nuclear Pore Complex Proteins - chemistry; Nuclear Pore Complex Proteins - metabolism; Nuclear Proteins - chemistry; Nuclear Proteins - metabolism; Saccharomyces cerevisiae; Structural Biology
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2015.09.047

The mechanisms by which intrinsically disordered proteins engage in rapid and highly selective binding is a subject of considerable interest and represents a central paradigm to nuclear pore complex (NPC) function, where nuclear transport receptors (NTRs) move through the NPC by binding disordered phenylalanine-glycine-rich nucleoporins (FG-Nups). Combining single-molecule fluorescence, molecular simulations, and nuclear magnetic resonance, we show that a rapidly fluctuating FG-Nup populates an ensemble of conformations that are prone to bind NTRs with near diffusion-limited on rates, as shown by stopped-flow kinetic measurements. This is achieved using multiple, minimalistic, low-affinity binding motifs that are in rapid exchange when engaging with the NTR, allowing the FG-Nup to maintain an unexpectedly high plasticity in its bound state. We propose that these exceptional physical characteristics enable a rapid and specific transport mechanism in the physiological context, a notion supported by single molecule in-cell assays on intact NPCs. [Display omitted] •Integrative structural biology reveals the basis of rapid nuclear transport•Transient binding of disordered nucleoporins leaves their plasticity unaffected•Multiple minimalistic low-affinity binding motifs create a polyvalent complex•A highly reactive and dynamic surface permits an ultrafast binding mechanism Intrinsically disordered nucleoporins (Nups) engage rapidly with nuclear transport receptors through many minimalistic, weakly binding motifs. These Nups form polyvalent complexes while retaining conformational plasticity thus ensuring both rapid and specific transport.