AJP - Gastrointestinal and Liver Physiology, Vol 254, Issue 4 580-G585, Copyright © 1988 by American Physiological Society

ARTICLES

Specific binding of lactoferrin to brush-border membrane: ontogeny and effect of glycan chain

L. A. Davidson and B. Lonnerdal
Department of Nutrition, University of California, Davis 95616.

Bioavailability of iron from human milk is exceptionally high. It has been suggested that lactoferrin, the major iron-binding protein in human milk, may participate in this high iron bioavailability from milk. We examined the interaction of lactoferrin with the intestinal brush-border membrane using the rhesus monkey as a model. Brush-border membrane vesicles were prepared from monkeys of various ages. Binding studies with 59Fe-labeled human and monkey lactoferrin were performed to examine interaction of lactoferrin with the brush-border membrane. Specific saturable binding of lactoferrin was found at all ages studied (fetal, suckling infant, weaned infant, juvenile, and adult). The dissociation constant for lactoferrin-receptor binding was 9 X 10(-6) M. In contrast, no binding of serum transferrin or bovine lactoferrin occurred. Removal of fucose from the lactoferrin glycans resulted in a significant decrease in binding. It was concluded that lactoferrin in milk may function in the process of iron absorption through interaction with a small intestinal receptor and that fucosylated glycans on the carbohydrate chain of lactoferrin are necessary for receptor recognition.

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