A designed mutant of the enzyme glutathione reductase shortens the crystallization time by a factor of forty.

The packing of glutathione reductase from Escherichia coli in crystal form T showed a place where two molecules are at a distance of only 6 A between the closest atoms, i.e. where a contact is almost made. In order to form this contact with hydrogen bonds, two amino-acid residues were exchanged. This mutation had no effect on molecular packing or the resolution limit of the X-ray diffraction, but facilitated crystal nucleation dramatically and possibly increased the crystal growth rate and shortened the crystallization time.