Fig. 2. Schematic drawing of the chimeric protein CB-EGFP. The cathepsin B portion of the chimeric protein consists of the signal peptide (S, light grey), the propeptide (pro, dark grey) and the light (LC, blue) and heavy chains (HC, blue) of the protease, which are covalently linked to EGFP (green) by a spacer peptide (pink). Exchanges of two amino acids within the propeptide of cathepsin B from FRTL-5 cells are indicated in grey, the positions of two potential N-glycosylation sites in orange and the active site residues of the cathepsin B portion of the chimeric protein are shown in blue. The complete coding sequence of the vector pCathB-EGFP is available from GenBank under accession number AF490378.