Induction of elongation factor Tu-GDP crystal polymorphism by polyethylene glycol contaminants

Trypsin-modified elongation factor (EF-)Tu-GDP from Escherichia coli is known to crystallize in several different unit cells under apparently identical conditions. The crystal polymorphism was investigated and found to be correlated with the source of polyethylene glycol used in the crystallization procedure. The use of highly purified polyethylene glycol promoted the growth of a new crystal form belonging to space group P2(1)2(1)2(1) with cell...