| First Author | Otsuka S | Year | 2008 |
| Journal | Proc Natl Acad Sci U S A | Volume | 105 |
| Issue | 42 | Pages | 16101-6 |
| PubMed ID | 18845677 | Mgi Jnum | J:248253 |
| Mgi Id | MGI:6093040 | Doi | 10.1073/pnas.0802647105 |
| Citation | Otsuka S, et al. (2008) Individual binding pockets of importin-beta for FG-nucleoporins have different binding properties and different sensitivities to RanGTP. Proc Natl Acad Sci U S A 105(42):16101-6 |
| abstractText | Importin-beta mediates protein transport across the nuclear envelope through the nuclear pore complex (NPC) by interacting with components of the NPC, called nucleoporins, and a small G protein, Ran. Although there is accumulated knowledge on the specific interaction between importin-beta and the Phe-Gly (FG) motif in the nucleoporins as well as the effect of RanGTP on this interaction, the molecular mechanism by which importin-beta shuttles across the nuclear envelope through the NPC is unknown. In this study, we focused on four binding pockets of importin-beta for the FG motifs and characterized the interaction using a single-molecule force-measurement technique with atomic-force microscopy. The results from a series of importin-beta mutants containing amino acid substitutions within the FG-binding pockets demonstrate that the individual FG-binding pockets have different affinities to FG-Nups (Nup62 and Nup153) and different sensitivities to RanGTP; the binding of RanGTP to the amino-terminal domain of importin-beta induces the conformational change of the entire molecule and reduces the affinity of some of the pockets but not others. These heterogeneous characteristics of the multiple FG-binding pockets may play an important role in the behavior of importin-beta within the NPC. Single-molecule force measurement using the entire molecule of an NPC from a Xenopus oocyte also implies that the reduction of the affinity by RanGTP really occurs at the nucleoplasmic side of the entire NPC. |
