Expression, purification and crystallization of Aspergillus nidulans NmrA,a negative regulatory protein involved in nitrogen-metabolite repression

The NmrA repressor protein of Aspergillus nidulans was overproduced in Esch erichia coli and purified to homogeneity. Gel-exclusion chromatography show ed that NmrA was monomeric in solution under the buffer conditions used. Th e protein was crystallized in three forms, belonging to trigonal, monoclini c and hexagonal space groups. Two of these crystal forms (A and B) diffract to high resolution and thus appear suitable for structure determination. C rystal form A belongs to space group P3((1))21, with unit-cell parameters a = b = 76.8, c = 104.9 Angstrom. Crystal form B belongs to space group C2, with unit-cell parameters a = 148.8, b = 64.3, c = 110.2 Angstrom, beta = 1 21.8 degrees.