Site specificity of iron removal from transferrin by alpha-ketohydroxypyridine chelators

The site specificity of the removal of iron from diferric human transferrin, at pH 7.4, by two alpha-ketohydroxypyridine chelators, 1,2-dimethyl-3-hydroxypyrid-4-one (L1) and mimosine, has been investigated using urea-polyacrylamide gel electrophoresis. Chelator L1 removes iron preferentially from the C-terminal site whereas mimosine shows a small preference for iron in the N-terminal site. The removal of iron has also been followed spectrophotometrically and by monitoring the loss of 59Fe from [59Fe]transferrin. Both chelators are able to remove iron completely from diferric transferrin without additional mediators or reducing agents.