Production and characterization of a novel tissue-type plasminogen activator derivative in Escherichia coli

We have created a novel thrombolytic agent by the combination of mutation with partial deletion of tissue-type plasminogen activator (t-PA). We constructed Escherichia coli expression vectors for (i) native t-PA (nt-PA) and its derivatives; (ii) K1K2P, consisting of kringle 1 (K1), kringle 2 (K2), and protease (P) domains; (iii) K2P, consisting of K2 and P domains; (iv) D-nt-PA; (v) D-K1K2P; and (vi) D-K2P. The latter three are point mutants of nt-PA, K1K2P, and K2P, respectively, in which Arg275 (number corresponds to that of nt-PA) has been mutated to Asp. The production of nt-PA and its derivatives was remarkably improved by (i) removal of the 3' noncoding region of nt-PA cDNA from expression vectors and (ii) expression in mutant E. coli derived from E. coli HB101, which is insensitive to heat-shock inductions. The proteins produced were precipitated as insoluble aggregates in the cells and were renatured to active forms by extraction with 8 M urea followed by dialysis against a redox buffer containing GSH and GSSG. The renaturation yield depended on the pH of the buffer and the number of disulfide bonds of the proteins (nt-PA << K1K2P < K2P). The mutation of Arg275 (the plasmin cleavage site) caused an increase in the catalytic enhancement by fibrin and a decrease of the interaction with plasminogen activator inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)