Complex binding of the embryonic interferon, ovine trophoblast protein-1, to endometrial receptors.
Ovine embryos produce an interferon (IFN)-alpha II in significant quantities during early pregnancy. This IFN, previously termed ovine trophoblast protein-1 (oTP-1), is a 172-amino-acid polypeptide which has been suggested to be the causal agent in maternal recognition of pregnancy in the ewe. Here we report the binding of oTP-1 and a recombinant bovine IFN-alpha I1 (rBoIFN-alpha I1; 165-166 amino acids long) to membrane preparations from ovine uterine endometrium. Both oTP-1 and rBoIFN-alpha I1 competed with each other for receptor binding. Based on Scatchard analysis, [125I]oTP-1 binding was determined to be complex and resolvable into a high-affinity (Kd = 3.8 x 10(-11) M, 30 fmoles/mg protein) and a low affinity (Kd = 1.7 x 10(-10) M; 96 fmoles/mg protein) component. Conversely [125I]rBoIFN-alpha I1 bound to only a single high-affinity receptor (Kd = 6.1 x 10(-11) M; 174 fmoles/mg protein). Cross-linking experiments using disuccinimidyl suberate revealed that [125I]oTP-1 associated with membrane polypeptides of two molecular weight classes (Mr 100,000 and 70,000), and could be displaced from both with rBoIFN-alpha I1. In contrast, [125I]rBoIFN-alpha I1 cross-linked to only the 100,000 Mr membrane polypeptide. These data provide evidence that the binding parameters of oTP-1 and rBoIFN-alpha I1 to endometrial receptors are different.
Hansen
T R
TR
Department of Animal Science, University of Missouri, Columbia 65211.
Kazemi
M
M
Keisler
D H
DH
Malathy
P V
PV
Imakawa
K
K
Roberts
R M
RM
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D004717:Endometrium / Q000378:metabolism*; D005260:Female; D007370:Interferon Type I / Q000378:metabolism*; D008566:Membranes; D011257:Pregnancy Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011869:Radioligand Assay; D011971:Receptors, Immunologic / Q000378:metabolism*; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D012756:Sheep / Q000196:embryology*; D013154:Spleen / Q000166:cytology
D007370:Interferon Type I; D011257:Pregnancy Proteins; D011971:Receptors, Immunologic; D017471:Receptors, Interferon; D011994:Recombinant Proteins; C020947:interferon tau