The purification and characterization of a metalloproteinase inhibitor (MI) from bovine aortic endothelial cells, and the demonstration that it is related to, but distinct from, tissue inhibitor of metalloproteinase (TIMP), have previously been reported [De Clerck, Y. A., Yean, T.-D., Ratzkin, B. J., Lu, H.S. & Langley, K. E. (1989) J. Biol. Chem. 264, 17445-17453]. The cDNA cloning of the bovine MI and its human homolog is now reported. The bovine cDNA cloning used probes designed on the basis of NH2-terminal amino acid sequence of bovine MI. The human cDNA cloning in turn used probes representing parts of the bovine cDNA nucleotide sequence. Both cDNAs encode leader sequences of 26 amino acids and mature protein sequences of 194 amino acids. The amino acid sequences of the mature proteins are 94% identical. The human MI cDNA was expressed in Escherichia coli, and a preparation containing anticollagenase activity was recovered. The amino acid sequence of mature human MI is 38% identical to the sequence for human TIMP, and the 12 cysteines in MI and TIMP are aligned almost identically. Thus MI and TIMP comprise an inhibitor family.

Boone, T. C., Johnson, M. J., De Clerck, Y. A., & Langley, K. E. (1990). cDNA cloning and expression of a metalloproteinase inhibitor related to tissue inhibitor of metalloproteinases. Proceedings of the National Academy of Sciences, 87(7), 2800–2804.