Comparison of MMP21 with MMP N3. The predicted signal peptide is underlined and the putative furin recognition sequences within the propeptide are in bold. The sequence in white on dark background indicates the unique insertion in the propeptide in MMP21. A unique cysteine residue in the catalytic domain is in bold and indicated with a black diamond below. Note that the sequence for Xl-MMP N3 is incomplete at the N-terminus. See Fig. 2 for other information.