A high-affinity folate binding protein in human amniotic fluid. Radioligand binding characteristics, immunological properties and molecular size.
The presence of a folate binding protein of high-affinity type (affinity constant 5.10(9) M-1, maximum folate binding 3 nM) in human amniotic fluid was demonstrated in equilibrium dialysis experiments (37 degrees C, pH 7.4) with the radioligand 3H-folate. Dissociation of 3H-folate from the binding protein was slow at pH 7.4 but rapid at pH 3.5. By use of rabbit antibodies against low molecular weight folate binding protein from human milk we determined the concentration of folate binding protein in 5 amniotic fluids (range 1.5-2.3 nM) in an Enzyme-Linked Immunosorbent Assay (ELISA). Ultrogel AcA 44 chromatography of amniotic fluid showed that immunoreactive and radioligand bound folate binding protein coeluted in two peaks: a major one (Mr approximately 25,000) and a minor one (Mr approximately 100,000).
Holm
J
J
Department of Clinical Chemistry, University of Tromsø, Norway.
Hansen
S I
SI
Høier-Madsen
M
M
D000653:Amniotic Fluid / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002850:Chromatography, Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000378:metabolism*; D006801:Humans; D008970:Molecular Weight; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000378:metabolism*; D011869:Radioligand Assay; D011956:Receptors, Cell Surface
D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D011257:Pregnancy Proteins; D011956:Receptors, Cell Surface; D005492:Folic Acid