Crystallization and preliminary X‐ray diffraction analysis of GCIP/HHM transcriptional regulator

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 Å resolution. Preliminary phase calculations using the data set obtained from the SeMet crystal suggested that the crystal belonged to space group P 3 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.