Isolation and function of a receptor for human lactoferrin in human fetal intestinal brush-border membranes

H. Kawakami, B. Lonnerdal

Research output: Contribution to journalArticle

161 Citations (Scopus)

Abstract

Iron absorption is known to be higher from human milk than from infant formula or bovine milk. The high bioavailability of human milk iron suggests that lactoferrin (Lf), the major iron-binding protein in human milk, may be a factor contributing to iron absorption in infants. We have isolated a human Lf receptor from solubilized human fetal intestinal brush-border membranes by affinity chromatography using immobilized human Lf. We also investigated the interaction of 125I-labeled human Lf and bovine Lf with brush-border membrane vesicles (BBMVs) from human small intestine using a rapid filtration technique. The molecular weight of the receptor was 110,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions and 37,000 under reducing conditions. Competitive binding studies demonstrated specific binding of human Lf. The binding was pH dependent, with an optimum between pH 6.5 and 7.5. Scatchard plot analysis indicated 4.3 x 1014 binding sites/mg membrane protein with an affinity constant of 0.3 x 106 M-1 for human Lf. Both half-Lf and deglycosylated Lf bound to the receptor with an affinity similar to intact Lf. In contrast, little binding of bovine Lf or human transferrin to human BBMVs occurred. These results suggest that the brush-border membrane receptor for human Lf may be responsible for the high iron absorption from human milk.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume261
Issue number5 24-5
StatePublished - 1991

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Lactoferrin
Microvilli
Membranes
Human Milk
Iron
Iron-Binding Proteins
lactoferrin receptors
Infant Formula
Competitive Binding
Transferrin
Affinity Chromatography
Sodium Dodecyl Sulfate
Biological Availability
Small Intestine
Polyacrylamide Gel Electrophoresis
Membrane Proteins
Milk
Molecular Weight
Binding Sites

Keywords

  • Intestinal absorption
  • Iron absorption
  • Lactoferrin receptor

ASJC Scopus subject areas

  • Physiology
  • Gastroenterology

Cite this

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abstract = "Iron absorption is known to be higher from human milk than from infant formula or bovine milk. The high bioavailability of human milk iron suggests that lactoferrin (Lf), the major iron-binding protein in human milk, may be a factor contributing to iron absorption in infants. We have isolated a human Lf receptor from solubilized human fetal intestinal brush-border membranes by affinity chromatography using immobilized human Lf. We also investigated the interaction of 125I-labeled human Lf and bovine Lf with brush-border membrane vesicles (BBMVs) from human small intestine using a rapid filtration technique. The molecular weight of the receptor was 110,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions and 37,000 under reducing conditions. Competitive binding studies demonstrated specific binding of human Lf. The binding was pH dependent, with an optimum between pH 6.5 and 7.5. Scatchard plot analysis indicated 4.3 x 1014 binding sites/mg membrane protein with an affinity constant of 0.3 x 106 M-1 for human Lf. Both half-Lf and deglycosylated Lf bound to the receptor with an affinity similar to intact Lf. In contrast, little binding of bovine Lf or human transferrin to human BBMVs occurred. These results suggest that the brush-border membrane receptor for human Lf may be responsible for the high iron absorption from human milk.",
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AB - Iron absorption is known to be higher from human milk than from infant formula or bovine milk. The high bioavailability of human milk iron suggests that lactoferrin (Lf), the major iron-binding protein in human milk, may be a factor contributing to iron absorption in infants. We have isolated a human Lf receptor from solubilized human fetal intestinal brush-border membranes by affinity chromatography using immobilized human Lf. We also investigated the interaction of 125I-labeled human Lf and bovine Lf with brush-border membrane vesicles (BBMVs) from human small intestine using a rapid filtration technique. The molecular weight of the receptor was 110,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions and 37,000 under reducing conditions. Competitive binding studies demonstrated specific binding of human Lf. The binding was pH dependent, with an optimum between pH 6.5 and 7.5. Scatchard plot analysis indicated 4.3 x 1014 binding sites/mg membrane protein with an affinity constant of 0.3 x 106 M-1 for human Lf. Both half-Lf and deglycosylated Lf bound to the receptor with an affinity similar to intact Lf. In contrast, little binding of bovine Lf or human transferrin to human BBMVs occurred. These results suggest that the brush-border membrane receptor for human Lf may be responsible for the high iron absorption from human milk.

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