A unique substrate binding mode discriminates membrane type-1 matrix metalloproteinase from other matrix metalloproteinases

In our study, we characterized the substrate recognition properties of membrane type-1 matrix metalloproteinase (MT1-MMP; also known as MMP-14), a key enzyme in tumor cell invasion and metastasis. A panel of optimal peptide substrates for MT1-MMP was identified using substrate phage display. The substrates can be segregated into four groups based on their degree of selectivity for MT1-MMP. Substrates with poor selectivity for MT1-MMP are comprised predominately of the Pro-X-X- down arrow -X-HY motif that is recognized by a number of MMP's. Highly selective substrates lack the characteristic Pro at the P-3 position; instead they contain an Arg at the P-4 position. This P-4 Arg is essential for efficient hydrolysis and for selectivity for MT1-MMP. Molecular modeling indicates that the selective substrates adopt a linear conformation that extends along the entire catalytic pocket of MT1-MMP, whereas non-selective substrates are kinked at the conserved P-3 Pro residue. Importantly, the selective substrates can be made nonselective by insertion of a proline kink at P-3, without significantly reducing overall k(cat)/K-m values. Altogether the study provides a structural basis for selective and non-selective substrate recognition by MT1-MMP. The findings in this report are likely to explain several aspects of MT1-MMP biology.