Localization of an antiviral site on the pregnancy recognition hormone, ovine trophoblast protein 1.
Ovine trophoblast protein 1 (oTP-1) is the interferon alpha (IFN-alpha) variant with potent antiviral activity and low toxicity that is responsible for maternal recognition of pregnancy in sheep. To examine the structure/function basis for the potent antiviral activity of oTP-1, we have exploited the direct approach of synthetic peptide competition with oTP-1 for receptor, using N-terminal oTP-1-(1-37) and C-terminal oTP-1-(139-172) peptides. These peptides possess structures similar to those predicted for the intact molecule on the basis of circular dichroism. oTP-1-(1-37) at 1.5 mM specifically blocked oTP-1 antiviral activity without affecting the antiviral activity of natural ovine IFN-alpha, recombinant bovine IFN-alpha, and recombinant human IFN-alpha. At concentrations as low as 0.15 mM, oTP-1-(139-172) blocked the antiviral activity of oTP-1, as well as that of natural ovine IFN-alpha, recombinant bovine IFN-alpha, and recombinant human IFN-alpha, but not recombinant bovine interferon gamma. Further, binding of radiolabeled oTP-1 to endometrial membrane preparations could be effectively inhibited by polyclonal anti-C-terminal and anti-N-terminal antisera, with the anti-C-terminal antiserum being the more effective inhibitor. Consistent with peptide and antiserum functional data, oTP-1 and recombinant bovine IFN-alpha are predicted to possess similar C-terminal structure but different N-terminal structure by composite surface profile predictions. The findings suggest that the C-terminal regions of IFN-alpha s bind to a common site on the IFN-alpha receptor while the N-terminal region binds to a site unique for the particular IFN-alpha.
Pontzer
C H
CH
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611.
Ott
T L
TL
Bazer
F W
FW
Johnson
H M
HM
D000595:Amino Acid Sequence; D000818:Animals; D000998:Antiviral Agents; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002942:Circular Dichroism; D004717:Endometrium / Q000378:metabolism; D005260:Female; D014644:Genetic Variation; D007106:Immune Sera; D007370:Interferon Type I; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology; D011487:Protein Conformation; D012756:Sheep; D014721:Vesicular stomatitis Indiana virus / Q000187:drug effects / Q000502:physiology; D014779:Virus Replication / Q000187:drug effects
D000998:Antiviral Agents; D007106:Immune Sera; D007370:Interferon Type I; D010455:Peptides; D011257:Pregnancy Proteins; C020947:interferon tau