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Updated: Jul 25, 2026

Isolation of Translating Ribosomes Containing Peptidyl-tRNAs for Functional and Structural Analyses
Published on: February 25, 2011
The GTP-binding protein Ran/TC4 is required for protein import into the nucleus
1Laboratory of Cell Biology, Howard Hughes Medical Institute, Rockefeller University, New York, New York 10021.
Abstract:
Two cytosolic fractions (A and B) from Xenopus oocytes are sufficient to support protein import into the nuclei of digitonin-permeabilized cells. Fraction A recognizes the nuclear localization sequence (NLS) and binds the import substrate to the nuclear envelope, whereas fraction B mediates the subsequent passage of the bound substrate into the nucleus. Here we report that two interacting components are required for full fraction-B activity, purify one of these components to homogeneity, and show that it is the highly abundant GTP-binding protein Ran (Ras-related nuclear protein)/TC4.
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