Search

Arg 121 was mutated to Ser and Glu in the N-terminal half-molecule of human lactoferrin to study the role of arginine residue in anion binding and iron binding. The two mutants, R121S and R121E, were expressed, purified and crystallized. Both mutants still bind iron but with decreased stability. The crystal structures indicated that destabilization of iron binding is caused by the disruption of the anion binding site. Mutation of Arg 121 eliminates one wall of the anion binding pocket and causes the synergistic carbonate ion to be displaced 0.5 angstrom from its location in the wild-type protein.