Abstract
GCIP/HHM is a human nuclear protein that is implicated in regulation of cell proliferation. Its primary structure contains helix-loop-helix and leucine-zipper motifs but lacks a DNA-binding basic region. Native and selenomethionine-derivatized (SeMet) crystals of full-length GCIP/HHM were obtained using the hanging-drop vapour-diffusion method. The crystals were greatly improved by adding tris(2-carboxyethyl)phosphine as a reducing reagent and diffracted to 3.5 A resolution. Preliminary phase calculations using the data set obtained from the SeMet crystal suggested that the crystal belonged to space group P3(2)21 and contained one molecule per asymmetric unit. Structure determination by the multiple-wavelength anomalous dispersion method using the SeMet crystals is in progress.