Molecular Cloning and Functional Expression of a Fibrinolytic Protease Gene from the Polychaeta, Periserrula Leucophryna

Full-length cDNA encoding a fibrinolytic protease (PLFP) from the cDNA library of the polychaete, Periserrula leucophryna was cloned, sequenced and expressed in Escherichia coli . The entire cDNA of the PLFP clone was 921 bp (CDS: 41-837), including a coding nucleotide sequence of 798 bp, a 5′-untranslaed region of 40 bp, and a 3′-noncoding region of 83 bp. The ORF encoded a 265-amino acid polypeptide precursor consisting of a 36-residue signal sequence and a 229-residue mature polypeptide. The sequence alignment results of PLFP revealed sequence similarity with several fibrinolytic enzymes. Sequence analysis revealed a conserved catalytic triad of His78, Asp126 and Ser219 residues, suggesting that PLFP is a serine protease. Mature PLFP had an apparent molecular weight of approximately 25 kDa and was produced in inclusion bodies when expressed in E. coli . Substrate specificity results that recombinant PLFP was active towards Arg-X or Lys-X and did not hydrolyze substrates with nonpolar amino acids at the P1 site. Recombinant PLFP was strongly inhibited by typical serine protease inhibitors, further indicating that PLFP is a member of the serine protease family. PLFP was able to dissolve artificial plasminogenfree fibrin, and its fibrinolytic behavior was similar to that of plasmin. Taken these results together, PLFP is a new member of the fibrinolytic enzyme family with selective specificity on fibrin, and the availability of PLFP offers an attractive alternative approach for thrombolysis therapy because rPLFP is believed to have advantages over currently used plasminogen activators, that is, lower price and lower side effect.