Expression of human cathepsin B protein in Escherichia coli

A cDNA fragment containing the coding sequence for the mature enzyme of human lysosomal proteinase cathepsin B was inserted in the pET plasmid expression vectors, so that it was placed under the control of transcription and translation signals from bacteriophage T₇. Upon induction, cathepsin B antigen was detected by in situ immunoscreening of lysed E. coli and by Western blot analysis of bacterial lysates. To our knowledge this is the first report of abundant synthesis of cloned cathepsin B in any expression system. Subfragments of cathepsin B can also be generated by this technique and will be used to study cathepsin B structure and function.