Purification of the plasmin receptor from human carcinoma cells and comparison to alpha-enolase

We have characterized a receptor for plasmin (Pli-R) from a human tumor cell line, MCF7MF. The Pli-R was purified from a MCF7 0.1% Triton X-100 solubilisate by affinity chromatography. A protein of 55-60 kDa was obtained, which bound plasminogen and plasmin specifically. Chemical cross-linking of M(r) 90 kDa [125I]-Pli to the surface of MCF7 cells with DSP results in the formation of a labelled complex of M(r) 145 kDa, suggesting a M(r) of 55-60 kDa for the receptor. Comparing Pli-R with alpha-enolase (a candidate for plasminogen receptor in U937 cells) we have found a high homology between both proteins, but not an identity.