Pg-R_KT on the monocyte/macrophage cell surface binds plasminogen (Pg) via interactions involving lysine binding sites on the Pg kringle domains with the C-terminal lysine residue on Pg-R_KT. The close proximity to uPA bound to the urokinase receptor (uPAR) greatly facilitates conversion of Pg to plasmin (Pm). Cell-associated Pm is involved in degradation of the extracellular matrix (ECM), cell migration, and in degrading fibrin.