Summary
A single-chain urokinase-type plasminogen activator (A431sc-uPA) was purified ˜18,000-fold
from A431 human epidermoid carcinoma cell supernatants by monoclonal antibody immunoaffinity
chromatography on 5B4-agarose and ion-exchange FPLC (overall yield 63%). More than
100 jig of A431sc-uPA can be recovered per liter of supernatant. The product is homogeneous
by SDS-PAGE and reverse phase FPLC analysis while two main isoelectric forms of pi
9.05 and pi 9.20 were observed by IEF. SDS-PAGE in reducing and non-reducing conditions,
Western blot analysis and zymography showed that A431sc-uPA is a single-chain protein
of about 50,000 Mr immunologically related to urokinase (uPA) and distinct from tissue
plasminogen activator (tPA). The N-terminal aminoacid sequence of A431sc-uPA (27 residues)
is identical to that of human kidney single-chain uPA. A431sc-uPA does not incorporate
3H-diisopropylfluorophosphate and is virtually inactive on the synthetic substrate
S-2444. Plasmin treatment converts A431sc-uPA into a two-chain active form with a
fibrinolytic specific activity of 123,000 I.U./mg.
Key words
Urokinase - Pro-urokinase - Plasminogen activator - Fibrinolysis - Monoclonal antibody