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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
Published on: May 3, 2018
Structural basis for cell-cycle-dependent nuclear import mediated by the karyopherin Kap121p
Junya Kobayashi1, Yoshiyuki Matsuura2
1Division of Biological Science, Graduate School of Science, Nagoya University, Japan.
Journal of Molecular Biology
|April 2, 2013
Summary
Kap121p, an essential protein, regulates nuclear import in yeast. Its unique inhibition during mitosis, driven by structural changes upon RanGTP binding, ensures proper cell division.
Area of Science:
- Cell biology
- Structural biology
- Molecular mechanisms of nuclear transport
Background:
- Kap121p (Pse1p) is a crucial karyopherin for nuclear import in Saccharomyces cerevisiae.
- Mitotic regulation involves arresting Kap121p import via nuclear pore complex rearrangements.
Purpose of the Study:
- To elucidate the structural basis of Kap121p-mediated nuclear import.
- To understand the regulatory mechanism of Kap121p during mitosis.
Main Methods:
- X-ray crystallography was used to determine structures of Kap121p.
- Structures were obtained for Kap121p alone, with cargoes, Nup53p, and RanGTP.
Main Results:
- Kap121p possesses a superhelical structure with 24 HEAT repeats.
- A novel nuclear localization signal (NLS) consensus sequence (KV/IxKx1-2K/H/R) was identified.
- Nup53p and cargo compete for the same binding site, explaining cargo release.
- RanGTP binding induces a conformation change, inhibiting NLS recognition.
Conclusions:
- Structural insights reveal Kap121p's cargo binding and regulation by Nup53p and RanGTP.
- The findings explain Kap121p's specific import inhibition during mitosis for cell cycle progression.
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