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The yeast nucleoporin Nsp1 binds nuclear localization sequences in vitro
Biochemistry and Cell Biology = Biochimie Et Biologie Cellulaire
|January 1, 1996
Summary
The yeast nucleoporin Nsp1 specifically binds nuclear localization sequences (NLSs) essential for protein transport into the nucleus. This binding, particularly by Nsp1 domains, is crucial for nuclear targeting, with affinities quantified for various NLSs.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Nuclear transport is a fundamental cellular process.
- Nuclear localization sequences (NLSs) mediate protein import into the nucleus.
- Specific interactions between NLSs and nuclear transport machinery are critical.
Purpose of the Study:
- To investigate the direct binding of the yeast nucleoporin Nsp1 to nuclear localization sequences (NLSs).
- To identify the domains of Nsp1 responsible for NLS binding.
- To characterize the binding affinity of Nsp1 for functional and mutant NLSs.
Main Methods:
- In vitro binding assays to study protein-NLS interactions.
- Characterization of Nsp1 domains for NLS binding sites.
- Determination of association constants for Nsp1-NLS interactions.
- Analysis of Nsp1 binding to mutant NLSs.
Main Results:
- The yeast nucleoporin Nsp1 specifically binds functional NLSs, including those from SV40 T-antigen and yeast Ga14.
- NLS binding sites on Nsp1 were localized to its N-terminal and middle repetitive regions.
- High association constants (1.2-5 x 10^7 M^-1) were determined for Nsp1-NLS interactions.
- Nsp1 exhibited significantly lower affinity for a poorly functional mutant NLS.
Conclusions:
- Nsp1 directly recognizes and binds nuclear localization sequences.
- Specific domains within Nsp1 are responsible for NLS recognition.
- The binding affinity of Nsp1 correlates with the in vivo nuclear targeting efficiency of NLSs.