Kringle domains have been found in plasminogen, hepatocyte growth factors, prothrombin, and apolipoprotein(a).

Kringles are found throughout the blood clotting and fibrinolytic proteins.

Kringle domains are believed to play a role in binding mediators (e.g., membranes, other proteins or phospholipids), and in the regulation of proteolytic activity.

[1][2][3] Kringle domains[4][5][6] are characterised by a triple loop, 3-disulfide bridge structure, whose conformation is defined by a number of hydrogen bonds and small pieces of anti-parallel beta-sheet.

They are found in a varying number of copies in some plasma proteins including prothrombin and urokinase-type plasminogen activator, which are serine proteases belonging to MEROPS peptidase family S1A.