On the affinity between the plasminogen activator inhibitor type 2 and apolipoprotein A1

The plasminogen activator inhibitor type 2 (PAI-2) is present in its high molecular weight, glycosylated form in pregnancy plasma. When the protein was purified from retroplacental blood by immunoaffiity chromatography on a PAI-2 anti body column and the retained material was further fractionated by gel filtration chromatography, it was always contaminated by apolipoprotein Al, the latter protein being identified by its N-terminal sequence, molecular weight in SDS-PAGE and immunological properties. The co-purification of the two proteins seemed to indicate a strong affinity between them, suggesting apolipoprotein A1 to be a carrier protein for this PAI-2 form. Further investigation to check this hypothesis showed that the binding of apolipoprotein A1 to the immunoaffinity support was PAI-2-independent and caused by a general surface affiity. This finding was corroborated by a study of the microtitre plate binding properties of the proteins. Pure, high molecular weight PA1 2 did not bind to apolipoprotein ...