The N-terminal domain I of human lactotransferrin binds specifically to phytohemagglutinin-stimulated peripheral blood human lymphocyte receptors.
Human lactotransferrin receptors have been recently characterized on mitogen-stimulated human lymphocytes [(1989) Eur. J. Biochem. 179, 481-487]. In order to define the lactotransferrin recognition site by these receptors, the binding to lymphocytes of several tryptic fragments, isolated from human lactotransferrin by mild tryptic hydrolysis [(1984) Biochim. Biophys. Acta 787, 90-96], has been investigated. The 30 kDa N-tryptic fragment (residues 4-281) and the re-associated N,C-tryptic complex bind to lactotansferrin lymphocyte receptor with a dissociation constant of 44 nM and 39 nM, respectively, similar to the value obtained for the native lactotransferrin (Kd = 46 nM). However, neither the N-terminal domain II (residues 91-257) nor the 50 kDa C-tryptic fragment (residues 282-703) are recognized. These results suggest that the binding site of human lactotransferrin by the lymphocyte receptor is located in the N-terminal lobe and more precisely in the N-terminal domain I (residues 4-90 and/or 258-281).
Rochard
E
E
Laboratoire de Chimie Biologique, CNRS no. 111, Université des Sciences et Techniques de Lille Flandres-Artois, Villeneuve d'Ascq, France.
Legrand
D
D
Mazurier
J
J
Montreuil
J
J
Spik
G
G
D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007781:Lactoferrin / Q000378:metabolism*; D007782:Lactoglobulins / Q000378:metabolism*; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D010835:Phytohemagglutinins / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014357:Trypsin
D007782:Lactoglobulins; D010446:Peptide Fragments; D010835:Phytohemagglutinins; D011956:Receptors, Cell Surface; C038340:lactoferrin receptors; D007781:Lactoferrin; D014357:Trypsin