CRYSTALLIZATION AND PRELIMINARY-X-RAY ANALYSIS OF AN ESCHERICHIA-COLIPURINE REPRESSOR HYPOXANTHINE DNA COMPLEX

The purine repressor (PurR) is a DNA-binding protein, which together w ith a purine corepressor serves to regulate de novo purine and pyrimid ine biosynthesis in Escherichia coli. PurR belongs to the structurally homologous lac repressor family of transcription regulators. A PurR-h ypoxanthine-DNA complex has been crystallized, with DNA encompassing t he high affinity purF operator site and which is 16 base-pairs long wi th 5'-deoxynucleoside overhangs on each complementary strand. The crys tals diffract to better than 2.6 Angstrom and take the orthorhombic sp ace group C222(1), with unit cell dimensions a=175.9 Angstrom, b=94.8 Angstrom and c=81.8 Angstrom. The structure determination of this PruR -hypoxanthine DNA complex will provide the first high resolution view of a Lacl member-DNA complex.