PURIFICATION, CRYSTALLIZATION AND PRELIMINARY-X-RAY ANALYSIS OF MURINE INTERLEUKIN-5

Wild-type and mutant forms of murine interleukin-5 (mIL-5) have been e xpressed in the baculovirus expression system, purified, and used in c rystallization trials. Attempts to obtain diffraction quality crystals of wild-type protein were unsuccessful. The substitution of glutamine for Asn75 preserved biological activity, while removing one of two pr edicted N-linked glycosylation sites, and the resulting protein was cr ystallized from polyethylene glycol 8000 at pH 7.8 in two crystal form s. The orthorhombic crystals, which belong to space group P2(1)2(1)2 w ith cell dimensions a = 55.9 Angstrom, b = 83.0 Angstrom and c = 52.3 Angstrom, diffract to beyond 2.5 Angstrom resolution. The second cryst al form belongs to a trigonal space group, either P3(1)21 or P3(2)21, with cell dimensions a = b = 62.1 Angstrom, c = 129.9 Angstrom, and di ffracts to about 3.8 Angstrom resolution. Each crystal form probably c ontains one mIL-5 dimer per asymmetric unit.