Riboflavin synthase of Escherichia coli - Effect of single amino acid substitutions on reaction rate and ligand binding properties

Conserved amino acid residues of riboflavin synthase from Escherichia coli were modified by site-directed mutagenesis. Replacement or deletion of phen ylalanine 2 afforded catalytically inactive proteins. S41A and H102Q mutant s had substantially reduced reaction velocities. Replacements of various ot her conserved polar residues had little impact on catalytic activity. F-19 NMR protein perturbation experiments using a fluorinated intermediate analo g suggest that the N-terminal sequence motif MFTG is part of one of the sub strate-binding sites of the protein.