Beta-2-glycoprotein 1 (APOH) (B2GP1)

Beta-2-glycoprotein 1 (B2GP1), also known as Apolipoprotein H, is a 50 kDa plasma glycoprotein that serves as a key autoantigen in Antiphospholipid Syndrome (APS). In its soluble form in the absence of anionic membranes like phosphatidylserine (PS), B2GP1 maintains a circular or closed conformation where Domain V interacts with Domain I (PMID: 10562333). This specific conformation masks the immunodominant epitope located on Domain I, preventing the binding of pathogenic autoantibodies (PMID: 22103525). Upon binding to negatively charged surfaces or PS exposed on activated cells, the protein undergoes a conformational transition to an open J-shape, exposing the Domain I epitope to the immune system (PMID: 23533224). This transition is a critical step in the development of thrombosis and pregnancy complications associated with APS. Therapeutic interventions are being explored to stabilize the circular conformation or use decoy molecules to block autoantibody interaction with the open form (UniProt P02749). Additionally, B2GP1 plays a role in the clearance of apoptotic debris and the regulation of the coagulation cascade (PMID: 26101214).

Other names

Apolipoprotein HAPOHB2-GPIBeta-2-glycoprotein IActivated protein C cofactorAPC inhibitor

Stabilization of the circular conformation, competitive inhibition of phospholipid binding, or direct blocking of the Domain I autoantibody epitope.