No abstract

A 25 kDa C-terminal tryptic fragment of elongation factor "Is has been purified to homogeneity. Experimental evidence suggests that the 25 kDa C-terminal and the 5.3 kDa N-terminal fragments are structurally independent domains. The N-terminal fragment is shown to be essential for the nucleotide exchange activity. Crystals of the C-terminal fragment belong to space group P2 or P21. The diffraction pattern shows a pronounced pseudo-C2 symmetry at low resolution. This pseudo symmetry increases when the crystals are irradiated with X-rays for a few hours.