Abstract
We have purified a cytosolic protein from Xenopus eggs that is essential for selective protein import into the cell nucleus. The purified protein, named importin, promotes signal-dependent binding of karyophilic proteins to the nuclear envelope. We have cloned, sequenced, and expressed a corresponding cDNA. Importin shows 44% sequence identity with SRP1p, a protein associated with the yeast nuclear pore complex. Complete, signal-dependent import into HeLa nuclei can be reconstituted by combining importin purified from Xenopus eggs or expressed in E. coli with Ran/TC4. Evidence for additional stimulatory factors is provided.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / pharmacology
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Amino Acid Sequence
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Animals
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Base Sequence
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Biological Transport / drug effects
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Cell Compartmentation*
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Cell Nucleus / metabolism*
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Cloning, Molecular
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Cytosol / chemistry*
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Cytosol / metabolism
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DNA, Complementary / genetics
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HeLa Cells
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Histocytochemistry
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Humans
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Karyopherins
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Molecular Sequence Data
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Nuclear Envelope / metabolism
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Ovum
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Protein Binding
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Recombinant Proteins / metabolism
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Sequence Analysis, DNA
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Sequence Homology, Amino Acid
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Sequence Homology, Nucleic Acid
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Xenopus
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alpha Karyopherins
Substances
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DNA, Complementary
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Karyopherins
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Nuclear Proteins
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Recombinant Proteins
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alpha Karyopherins
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Adenosine Triphosphate
Associated data
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GENBANK/L36339
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GENBANK/L36340