Karyopherin-centric control of nuclear pores based on molecular occupancy and kinetic analysis of multivalent binding with FG nucleoporins

Biophys J. 2014 Apr 15;106(8):1751-62. doi: 10.1016/j.bpj.2014.02.021.


Intrinsically disordered Phe-Gly nucleoporins (FG Nups) within nuclear pore complexes exert multivalent interactions with transport receptors (Karyopherins (Kaps)) that orchestrate nucleocytoplasmic transport. Current FG-centric views reason that selective Kap translocation is promoted by alterations in the barrier-like FG Nup conformations. However, the strong binding of Kaps with the FG Nups due to avidity contradicts rapid Kap translocation in vivo. Here, using surface plasmon resonance, we innovate a means to correlate in situ mechanistic (molecular occupancy and conformational changes) with equilibrium (binding affinity) and kinetic (multivalent binding kinetics) aspects of Karyopherinβ1 (Kapβ1) binding to four different FG Nups. A general feature of the FxFG domains of Nup214, Nup62, and Nup153 is their capacity to extend and accommodate large numbers of Kapβ1 molecules at physiological Kapβ1 concentrations. A notable exception is the GLFG domain of Nup98, which forms a partially penetrable cohesive layer. Interestingly, we find that a slowly exchanging Kapβ1 phase forms an integral constituent within the FG Nups that coexists with a fast phase, which dominates transport kinetics due to limited binding with the pre-occupied FG Nups at physiological Kapβ1 concentrations. Altogether, our data reveal an emergent Kap-centric barrier mechanism that may underlie mechanistic and kinetic control in the nuclear pore complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Glycine / analogs & derivatives*
  • Glycine / metabolism
  • Humans
  • Kinetics
  • Models, Molecular
  • Nuclear Pore / metabolism*
  • Nuclear Pore Complex Proteins / chemistry*
  • Nuclear Pore Complex Proteins / metabolism*
  • Protein Binding
  • Protein Structure, Tertiary
  • Surface Plasmon Resonance
  • Xenopus laevis
  • beta Karyopherins / metabolism*


  • KPNB1 protein, human
  • Nuclear Pore Complex Proteins
  • beta Karyopherins
  • 2-phenylglycine
  • Glycine