Wei-Li Hu1, Joël Mazurier1, G Sawatzki2, J Montreuil1, Geneviève Spik1
1Laboratoire de Chimie Biologique de l'Université des Sciences et Techniques de Lille Flandres-Artois, Unité Associée au CNRS n° 217et Laboratoire Pilote du Ministére de l'Education Nationale, 59655 Villeneuve d'Ascq Cédex, France
2Abteilung für Transfusions Medizin der Universität, D-7900 Ulm, Donau, Federal Republic of Germany
Tóm tắt
A specific lactotransferrin receptor was identified in the mouse small-intestinal brush-border membrane and the binding features were investigated in homologous and heterologous systems. The receptor was found to be specific for lactotransferrins isolated from milk of various species, but the affinity was higher toward the homologous ligand (Ka = 3.5 x 10(6) M-1 compared with 2.6 x 10(6) M-1 for both human and bovine lactotransferrins). However, the number of binding sites (n) was the same for the three lactotransferrins, namely 0.53 x 10(12)/micrograms of membrane protein. The binding of mouse lactotransferrin to its receptor was found to be pH-dependent, with an optimal binding at pH 5.5, and seemed unlikely to be carbohydrate-mediated. The receptor was demonstrated to be devoid of any affinity for human and mouse serotransferrins or for a ‘serotransferrin-like’ protein isolated from mouse milk. The receptor was solubilized with 1% Triton X-100 with good yield. The solubilized receptor was found to retain lactotransferrin-binding activity and sensitivity to pH.
