Abstract
The receptor for human urokinase-type plasminogen activator (u-PA) was purified from phorbol 12-myristate 13-acetate-stimulated U937 cells by temperature-induced phase separation of detergent extracts, followed by affinity chromatography with immobilized diisopropyl fluorophosphate-treated u-PA. The purified protein shows a single 55-60 kDa band after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining. It is a heavily glycosylated protein, the deglycosylated polypeptide chain comprising only 35 kDa. The glycosylated protein contains N-acetyl-D-glucosamine and sialic acid, but no N-acetyl-D-galactosamine. Glycosylation is responsible for substantial heterogeneity in the receptor on phorbol ester-stimulated U937 cells, and also for molecular weight variations among various cell lines. The amino acid composition and the NH2-terminal amino acid sequence are reported. The protein has a high content of cysteine residues. The NH2-terminal sequence is not closely related to any known sequence. The identification of the purified and sequenced protein with the human u-PA receptor is based on the following findings: 1) the ability of the purified protein to bind u-PA and its amino-terminal fragment; 2) the identical electrophoretic mobilities observed for cross-linked conjugates, formed between either the purified protein or the u-PA receptor on intact U937 cells and the above ligands; 3) the identity of the apparent molecular weight of the purified protein to that predicted for the u-PA receptor in the same cross-linking studies; 4) the identical extent of glycosylation of the purified protein and of the u-PA receptor in crude membrane fractions, as detected after cross-linking; 5) the ability of antibodies raised against the purified protein to inhibit cellular binding of the amino-terminal fragment of u-PA.
Original language | English |
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Journal | The Journal of Biological Chemistry |
Volume | 265 |
Issue number | 11 |
Pages (from-to) | 6453-60 |
Number of pages | 8 |
ISSN | 0021-9258 |
Publication status | Published - 15 Apr 1990 |
Externally published | Yes |
Keywords
- Amino Acid Sequence
- Amino Acids
- Cell Line
- Chromatography, Affinity
- Electrophoresis, Polyacrylamide Gel
- Enzyme Precursors
- Genetic Variation
- Glycosylation
- Humans
- Molecular Sequence Data
- Molecular Weight
- Receptors, Cell Surface
- Receptors, Urokinase Plasminogen Activator
- Tetradecanoylphorbol Acetate
- Urokinase-Type Plasminogen Activator
- Journal Article
- Research Support, Non-U.S. Gov't