Probing the potential metal binding site in Escherichia coli 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (phenylalanine-sensitive)

The active site residues of the proposed metal binding site of DAH 7-P synt hase (phe) were probed by site-directed mutagenesis of C61 to glycine and s erine, H64 to glycine, and with the double mutant C61H/H64C, While C61S and C61H/ H64C were inactive, both C61G and H64G were active. All mutants, reg ardless of enzymatic activity, bound one equivalent of Fe2+ per monomeric u nit. Even though C61 and H64 were shown not to be metal ligands for the DAH 7-P synthase (phe), they may provide some of the backbone interactions/sec ondary structural elements necessary to properly form the metal binding poc ket. (C) 1998 Federation of European Biochemical Societies.