Interaction of Matrix Metalloproteinases-2 and -9 with Pregnancy Zone Protein and α2-Macroglobulin

The binding of matrix metalloproteinases-2 and -9 to pregnancy zone protein and α2-macroglobulin was studied. The binding was demonstrated by formation of dimeric as well as tetrameric complexes of pregnancy zone protein and by the formation of α2-macroglobulin complexes with fast and intermediate mobility in native gel electrophoresis. The complex formation was confirmed by the use of125I-labeled matrix metalloproteinase-2. The cleavage sites in the “bait” regions following formation of high-molecular-weight complexes of matrix metalloproteinases with the α-macroglobulins were determined by protein sequence analysis. Pregnancy zone protein was cleaved at Thr693-Tyr694and α2-macroglobulin at Gly679-Leu680and Arg696-Leu697by matrix metalloproteinase-2. Matrix metalloproteinase-9 cleaved α2-macroglobulin at the same site as matrix metalloproteinase-2, but cleavage of pregnancy zone protein was at Leu753-Ser754. The sequences of the bands, visualized in the SDS gel, of approximately 90 and 165 kDa or higher molecular weight complexes were the same. This indicates that the matrix metalloproteinases cleaved the inhibitors with or without binding to them. The present results suggest that matrix metalloproteinases-2 and -9 may interact with pregnancy zone protein and α2-macroglobulinin vivo.