Sequence and characterization of cytoplasmic nuclear protein import factor p97

Neil C. Chi, Ermoné J.H. Adam, Stephen A. Adam*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

246 Scopus citations


Nuclear location sequence-mediated binding of karyophilic proteins to the nuclear pore complexes is one of the earliest steps in nuclear protein import. We previously identified two cytosolic proteins that reconstitute this step in a permeabilized cell assay: the 54/56-kD NLS receptor and p97. A monoclonal antibody to p97 localizes the protein to the cytoplasm and the nuclear envelope. p97 is extracted from nuclear envelopes under the same conditions as the O-glycosylated nucleoporins indicating a tight association with the pore complex. The antibody inhibits import in a permeabilized cell assay but does not affect binding of karyophiles to the nuclear pore complex. Immunodepletion of p97 renders the cytosol inactive for import and identifies at least three other cytosolic proteins that interact with p97. cDNA cloning of p97 shows that it is a unique protein containing 23 cysteine residues. Recombinant p97 binds zinc and a bound metal ion is required for the nuclear envelope binding activity of the protein.

Original languageEnglish (US)
Pages (from-to)265-274
Number of pages10
JournalJournal of Cell Biology
Issue number2
StatePublished - Jul 1995

ASJC Scopus subject areas

  • Cell Biology


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