Patent ID: 7455987

Claim:
A process for selecting a signal peptide for secretory expression of a desired hirudin or hirudin derivative protein in E. coli , comprising: (a) expressing in E. coli in culture medium, hirudin or a hirudin derivative which has antithrombotic activity, and which has a defined amino acid, aa x , at its N terminus, wherein said amino acid is connected via its N-terminal to a test signal peptide; (b) determining expression rate by measuring said hirudin or hirudin derivative activity in the culture supernatant; (c) repeating steps (a) and (b) with various signal peptides; (d) selecting said signal peptide by comparing the expression rates represented by the hirudin or hirudin derivative antithrombotic activity found in step (b) wherein the E. coli bacteria are not E. coli secretor mutants.