Crystallization and preliminary X-ray analysis of human RCC1, the regulator of chromosome condensation

RCC1, the regulator of chromosome condensation, is the guanine nucleotide-e xchange factor (GEF) of the GTP-binding protein Ran. Its GEF activity on Ra n makes it a key element in nucleo-cytoplasmic transport and cell-cycle reg ulation. Crystals of human RCC1 suitable for X-ray analysis have been obtai ned using the seeding technique in hanging drops with sodium citrate as a p recipitant. The crystals diffract to 1.7 Angstrom at 100 K and belong to th e space group Pl,with unit-cell parameters a = 49.5, b = 84.3, c = 84.9 Ang strom, alpha = 113.0, beta = 103.9, gamma = 103.3 degrees. The Matthews par ameter (V-m) and the self-rotation function are consistent with three molec ules in the unit cell, which is confirmed by the averaged single isomorphou s replacement (SIR) electron-density map.