Purification of Ran-interacting protein that is required for protein import into the nucleus

P10 is the new and second protein essential for the activity of fraction B in transporting proteins to the digitonin-permeabilized cell nuclei of Xenopus ovary. Gel filtration chromatography and SDS/PAGE methods indicate that the peptide sequence of P10 is similar to the human placental protein 15 and to the protein product of Saccharomyces cerevisiae open reading frame. P10 fractionates with a size of 30 kDa but exhibits a 10 kDa molecular mass with gel chromatography. P10 coordinates with the first protein GTPase ras-related nuclear protein to enhance fraction B activity.