Polymorphism in crystalline elongation factor Tu · GDP from Escherichia coli

Abstract

Native Escherichia coli elongation factor Tu · GDP crystallizes from polyethylene glycol 6000 in four trigonal and hexagonal crystal forms. Two additional forms have been produced by solid state transitions. Assuming certain specific asymmetric associations, all six crystal forms can be derived from the packing arrangement within a master space group P6 2,422. Slight rearrangements allow a further pseudotetragonal form to be included in this scheme. Crystals with space group P3 1,221 can be grown larger than 500 μm in diameter. They diffract X-rays to a resolution of at least 2.8 Å. Several lines of evidence indicate that they have two molecular sites per asymmetric unit and that half of these sites are occupied. If this occupation is random, then these crystals are suitable for a detailed structure analysis. The analysis would be simplified if crystals with the master space group P6 2,422, which has been produced by a solid state transition, could be obtained routinely.