Identification of lactoferrin-binding proteins in human serum.

摘要

The iron-binding protein lactoferrin is present in virtually all mammalian exocrine fluids and in blood. Blood lactoferrin originates from neutrophils and is cleared from the circulation by hepatocytes. The interaction of lactoferrin with its receptor on hepatocytes, the asialoglycoprotein receptor, is modulated by serum. The purpose of this study was to identify and characterize serum proteins that bind to lactoferrin. Bovine and human sera were fractioned by salt precipitation, ion-exchange chromatography, and by lactoferrin-agarose affinity chromatography. Several lactoferrin-binding proteins were purified from bovine and human sera, and human serum lactoferrin-binding proteins were subjected to sequence analysis. Four human lactoferrin-binding proteins identified included ceruloplasmin, complement C4, alpha-2-macroglobulin, and immunoglobulin G. Each of these proteins bound lactoferrin non-covalently and independent of each other. These studies demonstrate that lactoferrin binds multiple serum proteins and may influence the activity of these serum proteins in iron metabolism and host defense.