Elasticity of Nsp1 and Its Binding with Kap95 Probed by Single Molecule Force Spectroscopy

Nuclear pore complexes (NPC) facilitate receptor-mediated translocation of proteins and ribonucleoprotein complexes between the nucleus and the cytoplasm in eukaryotic cells. Small molecules can move through the NPC via passive diffusion, but the translocation of cargo proteins larger than ~40 kD generally requires specific transport receptor molecules collectively termed karyopherins (Kaps). The translocation of Kap-cargo complexes occurs due to specific binding between Kaps and integral NPC proteins called nucleoporins that contain degenerate multiple repeats of “Phe-Gly” and are called FG-Nups. Nsp1 is an FG-Nup located at the entrance and exit of the NPC. This work focuses on the preparation and nano-mechanical characterization of surface tethered Nsp1 using Atomic Force Microscopy. Using single molecule force spectroscopy, we probe the stretching, flexibility and Kap-binding characteristics of Nsp1. Knowing the elastic properties of Nsp1 should provide insight into the mechanisms of binding with Kap95 complexes and the transport of large cargo molecules through the Nuclear Pore Complex.