sitting-drop vapour-difusion method. Four different crystal forms of Uox are analyzed. In the presence of uracil and 5,6-diaminouracil crystals usually belong to the trigonal space group P3(1)21, the asymmetric unit of which contains one tetramer of Uox. Chemical oxidation of 5,6-diaminouracil within the protein may occur, leading to the canonical (I222) packing with one subunit per asymmetric unit. Coexistence of two crystal forms, P2(1) with two tetramers per asymmetric unit and I222, is found in the same crystallization drop containing another inhibitor, guanine. A fourth form, P2(1)2(1)2 with one tetramer per asymmetric unit, results in the presence of cymelarsan, an additive |
Aspergillus flavus |