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Importin-beta-like nuclear transport receptors
1Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720-3200, USA.
Genome Biology
|June 26, 2001
Summary
Nuclear transport receptors, importins and exportins, mediate macromolecule movement across the nuclear envelope. These proteins are regulated by the small GTPase Ran, facilitating cargo transport into or out of the nucleus.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Macromolecular transport across the nuclear envelope is crucial for cellular function.
- Numerous soluble transport receptors mediate nuclear import and export.
- Most receptors belong to the importin beta (karyopherin beta) family.
Purpose of the Study:
- To elucidate the mechanisms of nuclear transport mediated by importins and exportins.
- To understand the role of the small GTPase Ran in regulating these processes.
Main Methods:
- Identification and classification of importin-beta superfamily members.
- Analysis of interactions between transport receptors, cargo, and Ran.
- Investigation of RanGTP's role in cargo release.
Main Results:
- The importin-beta superfamily comprises at least 22 members in humans and 14 in yeast.
- Importins and exportins are regulated by the small GTPase Ran, which is GTP-bound in the nucleus.
- Importins bind cargo in the cytoplasm and release it in the nucleus upon RanGTP binding.
- Exportins bind cargo in the nucleus in a RanGTP-dependent manner and release it in the cytoplasm after GTP hydrolysis.
Conclusions:
- Importin-beta-like transport factors shuttle between the nucleus and cytoplasm.
- These factors interact with RanGTP and recognize specific transport substrates.
- Understanding these transport mechanisms is key to comprehending nuclear envelope function.