Model depicting the role of S100A10 in endothelial cell plasmin generation. The predominant form of S100A10 at the endothelial cell surface is as a heterotetramer, AIIt, which consists of 2 copies each of the annexin A2 and S100A10 subunits.²²  The annexin A2 subunit acts as a regulatory subunit, which uses its phospholipid-binding sites to anchor S100A10 to the cell surface. The S100A10 subunit binds tPA and Pg at the carboxyl-terminal lysine residue.^18,19  The colocalization of tPA and Pg results in accelerated cleavage of Pg by tPA, resulting in Pm generation and fibrinolytic activity.