Metal-combining properties of human lactoferrin. The effect of nitration of lactoferrin with tetranitromethane.

When iron . lactoferrin and apolactoferrin were submitted to nitration with tetranitromethane, the number of unmodified tyrosine residues recovered upon acid hydrolysis was 4-5 in the former case against 0-1 in the latter. The iron-binding capacity of lactoferrin appeared to remain intact following nitration of the iron-containing form of the protein, whereas metal-combining properties were destroyed when apolactoferrin was treated similarly. Tetranitromethane was found to cause changes in lactoferrin that went far beyond the mere nitration of a few tyrosine residues. Much of the tyrosine was destroyed and the same applied to t.ryptophan, part of which was converted to unidentified reaction products.