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Figure 1 | BMC Medicine

Figure 1

From: What does matrix metalloproteinase-1 expression in patients with breast cancer really tell us?

Figure 1

Domain structures of secreted and membrane-anchored MMPs. The basic organizations of human MMP family members are depicted: S, signal peptide; Pro, pro-peptide; Cat, catalytic domain, containing cysteine group (C);Zn, zinc ion; Fn, fibronectin-II- like repeats; Hpx, hemopexin like domain; TM, transmembrane domain; GPI, glycol-phosphatidylinositol membrane anchor; C, cytoplasm tail; CA, cysteine array; Ig, immunoglobulin-like domain; the flexible linker or hinge region is represented by a wavy black ribbon. The domain structure includes the signal peptide, which guides the enzyme into the endoplasmic reticulum during synthesis, the propeptide domain, which sustains the latency of MMPs, the catalytic domain, which houses the Zn2+ region and is responsible for enzyme activity, the hemopexin domain, which determines the substrate specificity, and a small hinge region. Additional transmembrane and intracellular domains are also present: the hinge region in MMP-9 is heavily O-glycosylated; the furin-activated MMPs and all of the membrane-anchored MMPs have a basic motif at the C-terminal end of their prodomains;; the two gelatinases (MMP-2 and -9) contain three fibronectin-II-like repeats; four of the six MT-MMPs are anchored to the cell membranes through a type I transmembrane domain and the other two through a glycosylphosphatidylinositol moiety. The membrane-anchored MMP-23, has an N-terminal type II transmembrane domain. The two minimal domain MMPs and MMP-23 lack the HPX domain and, in the latter enzyme, this domain is replaced by a C-terminal cystein array (Ca) and an immunoglobulin-like (Ig) domain. MMPs are produced in a latent form and most are activated by extracellular proteolytic cleavage of the propeptide and finely regulated by the tissue inhibitors of metalloproteinases (TIMP)[9].

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