Crystallization and preliminary crystallographic analysis of E. coli uridine 5'-diphospho-N-acetylenolpyruvylglucosamine reductase in two new crystal forms.
Uridine 5'-diphospho-N-acetylenolpyruvylglucosamine reductase (MurB), the second enzyme in the peptidoglycan synthetic pathway of Escherichia coli, has been crystallized in two previously unreported forms, one orthorhombic and the other monoclinic. MurB (molecular mass 38 kDa) crystallizes in a range of conditions that utilize polyethylene glycol fractions as precipitants, and crystals can be grown with or without the enzyme's substrate, uridine 5'-diphospho-N-acetylenolpyruvylglucosamine. X-ray diffraction from crystals of the orthorhombic form extends to 2 A resolution and shows the symmetry and systematic absences of space group P2(1)2(1)2(1). These crystals show significant variations in cell dimensions at room temperature and at 100 K. A crystal used to collect a 2.0 A resolution data set at a synchrotron source showed cell dimensions at ca 100 K of a = 51.0, b = 79.3 and c = 87.1 A, indicating one molecule peroasymmetric unit. The monoclinic crystals scatter X-rays to 3.0 A resolution consistent with space group P2(1), unit-cell dimensions (ca 100 K) a = 50.7, b = 92.4, c = 85.5 A, and beta = 104 degrees, and two molecules per asymmetric unit. Mercury derivatives have been prepared with both orthorhombic and monoclinic forms, and efforts are underway to exploit these derivatives to determine the structure of this protein.