We have identified and characterized a novel human tissue inhibitor of metalloproteinase
(TIMP). It is found exclusively in the extracellular matrix of a large number of cultured
human cells, including: primary embryonal kidney (293), neuroblastoma (SK-N-SH), normal
whole embryo (FHs 173We), cervical carcinoma (HeLa S3), colon adenocarcinoma (Caco-2),
ileocecal adenocarcinoma (HCT-8), fibrosarcomas (SW 684 and Hs 913T) and normal gingival
fibroblasts (GF11 and 1292). It was not detected in the conditioned media from any
of these cell lines. Its apparent molecular mass of 24-25 kDa, as determined by its
migration on protease-substrate gels, is intermediate between TIMP-1 (28.5 kDa) and
TIMP-2 (21 kDa). Like the latter two proteins, human TIMP-3 contains intrachain disulfide
bonds and displays altered electrophoretic mobility in the presence of beta-mercaptoethanol.
The N-terminal, amino acid sequence of the protein is identical to that of chicken
TIMP-3 (ChIMP-3), and its amino acid composition is similar. The protein is not N-glycosylated,
as determined by treatment with N-glycosidase-F. Finally, it is recognized by antisera
raised against pure ChIMP-3 but not by anti-human TIMP-1 or anti-human TIMP-2 antibodies.
Based on these properties, we propose that this protein is TIMP-3 and is the human
counterpart of ChIMP-3 (Pavloff et al., J. Biol. Chem. 267: 17321-17326, 1992). Two
additional inhibitors detected in the matrix of human cell lines, designated inhibitor
of metalloproteinase (IMP)-a and IMP-b, migrate with apparent masses of 29 kDa and
30 kDa. Both are N-glycosylated. A fourth inhibitor activity, which is smaller in
mass than TIMP-3 and is also pecifically located in the matrix, is detectable in some
cell lines.