Identification of angiotensinogen and complement C3dg as novel proteins binding the proform of eosinophil major basic protein in human pregnancy serum and plasma.
In sera from pregnant women, pregnancy-associated plasma protein-A (PAPP-A) circulates as a disulfide-bound complex (approximately 474 kDa) with the proform of eosinophil major basic protein (proMBP) (Oxvig, C., Sand, O., Kristensen, T., Gleich, G. J., and Sottrup-Jensen, L. (1993) J. Biol. Chem. 268, 12243-12246). We have produced monoclonal antibodies (mAbs) against the PAPP-A.proMBP complex and established a radioimmunoassay utilizing a mAb recognizing the PAPP-A subunit. Surprisingly, serum levels of proMBP exceed those of PAPP-A four to 10-fold on a molar basis throughout pregnancy. This result prompted an investigation of the status of proMBP in pregnancy. Using a proMBP-specific mAb two novel proMBP complexes have been isolated by chromatographic techniques. Based on sequence analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and reaction with specific antibodies, one is shown to be a 2:2 disulfide-bound complex (approximately 200 kDa) between proMBP and angiotensinogen. The other is a 2:2:2 complex (approximately 300 kDa) between proMBP, angiotensinogen, and complement C3dg. Circulating proMBP in pregnancy is thus present in three types of complexes. These results suggest that specific interactions between the complexed proteins occur in pregnancy, and the possibility is raised that their interactions are important in the pathophysiology of pregnancies associated with hypertension.
Oxvig
C
C
Department of Molecular Biology, University of Aarhus, Denmark.
Haaning
J
J
Kristensen
L
L
Wagner
J M
JM
Rubin
I
I
Stigbrand
T
T
Gleich
G J
GJ
Sottrup-Jensen
L
L
D000595:Amino Acid Sequence; D000808:Angiotensinogen / Q000378:metabolism*; D000818:Animals; D001798:Blood Proteins / Q000302:isolation & purification / Q000378:metabolism*; D003179:Complement C3b / Q000378:metabolism*; D047091:Eosinophil Granule Proteins; D005260:Female; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism*; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy / Q000097:blood*; D011257:Pregnancy Proteins / Q000378:metabolism*; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D011498:Protein Precursors / Q000378:metabolism*; D012260:Ribonucleases
D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D010446:Peptide Fragments; D011257:Pregnancy Proteins; D011498:Protein Precursors; C045477:complement C3d,g; D000808:Angiotensinogen; D003179:Complement C3b; D012260:Ribonucleases; D011266:Pregnancy-Associated Plasma Protein-A