Crystallization and preliminary X-ray diffraction studies of an inactive mutant aspartate transcarbamoylase from Escherichia coli.

A mutant aspartate transcarbamoylase, ATCase231, has been crystallized at neutral pH. The mutant enzyme has a single substitution of aspartic acid in place of glycine within the catalytic chain and shows not only the loss of enzyme activity but also marked changes in the chemical reactivity of several amino acid residues and weakening of interaction between regulatory and catalytic subunits. Despite these differences, the mutant enzyme crystals have the same space group and cell parameters as the wild type crystals grown at pH 5.9.