Secondary literature sources for the HX domain

For each of the hand selected primary papers associated with the HX domain, 100 neighbouring papers are retrieved from PubMed. If one of these neighbouring papers is referenced by more than two primary papers, it is shown in the table below.

Molecular regulation of cellular invasion--role of gelatinase A and TIMP-2.

Yu AE, Hewitt RE, Kleiner DE, Stetler-Stevenson WG
Biochem Cell Biol. 1996; 74: 823-31

Extracellular matrix (ECM) turnover is an event that is tightly regulated. Much of the coordinate (physiological) or discoordinate (pathological) degradation of the ECM is catalyzed by a class of proteases known as the matrix metalloproteinases (MMPs) or matrixins. Matrixins are a family of homologous Zn atom dependent endopeptidases that are usually secreted from cells as inactive zymogens. Net degradative activity in the extracellular environment is regulated by specific activators and inhibitors. One member of the matrixin family, gelatinase A, is regulated differently from other MMPs, suggesting that it may play a unique role in cell-matrix interactions, including cell invasion. The conversion from the 72 kDa progelatinase A to the active 62 kDa species may be a key event in the acquisition of invasive potential. This discussion reviews some recent findings on the cellular mechanisms involved in progelatinase A activation and, in particular, the role of tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) and transmembrane containing metalloproteinases (MT-MMP) in this process.

The hemopexin-like domain (C domain) of human gelatinase A (matrix metalloproteinase-2) requires Ca2+ for fibronectin and heparin binding. Binding properties of recombinant gelatinase A C domain to extracellular matrix and basement membrane components.

Wallon UM, Overall CM
J Biol Chem. 1997; 272: 7473-81

The binding properties of the COOH-terminal hemopexin-like domain (C domain) of human gelatinase A (matrix metalloproteinase-2, 72-kDa gelatinase) were investigated to determine whether the C domain has binding affinity for extracellular matrix and basement membrane components. Recombinant C domain (rC domain) (Gly417-Cys631) was expressed in Escherichia coli, and the purified protein, identified using two antipeptide antibodies, was determined by electrospray mass spectrometry to have a mass of 25,925 Da, within 0.1 Da of that predicted. As assessed by microwell substrate binding assays and by column affinity chromatography, the matrix proteins laminin, denatured type I collagen, elastin, SPARC (secreted protein that is acidic and rich in cysteine), tenascin, and MatrigelTM were not bound by the rC domain. Unlike the hemopexin-like domains of collagenase and stromelysin, the rC domain also did not bind native type I collagen. Nor were native or denatured types II, IV, V, and X collagen, or the NC1 domain of type VII collagen bound. However, binding to heparin and fibronectin (Kd, 1.1 x 10(-6) M) could be disrupted by 0.58-0.76 and 0.3 M NaCl, respectively. Using nonoverlapping chymotrypsin-generated fragments of fibronectin, binding sites for the rC domain were found on both the 40-kDa heparin binding and the 120-kDa cell binding fibronectin domains (Kd values, approximately 4-6 x 10(-7) M). The Ca2+ ion, but not the potential structural Zn2+ ion, were found to be essential for maintaining the binding properties of the protein. The apo-form of the rC domain did not bind heparin, and both ethylenediaminetetraacetic acid and the specific Ca2+ ion chelator 1, 2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid, but not the Zn2+ ion chelator 1,10-phenanthroline, eluted the holo form of the rC domain from both heparin-Sepharose and fibronectin. Inductive coupled plasma mass spectrometry also did not detect a Zn2+ ion in the rC domain. In contrast, reduction with 65 mM dithiothreitol did not interfere with heparin binding, further emphasizing the crucial structural role played by the Ca2+ ion. Together, these data demonstrate for the first time that the hemopexin-like domain of gelatinase A has a binding site for fibronectin and heparin, and that Ca2+ ions are important in maintaining the structure and function of the domain.

The heparin binding 25 kDa fragment of thrombospondin-1 promotes angiogenesis and modulates gelatinase and TIMP-2 production in endothelial cells.

Taraboletti G, Morbidelli L, Donnini S, Parenti A, Granger HJ, Giavazzi R, Ziche M
FASEB J. 2000; 14: 1674-6

Human 92 kDa type IV collagenase: functional analysis of fibronectin and carboxyl-end domains.

Strongin AY, Collier IE, Krasnov PA, Genrich LT, Marmer BL, Goldberg GI
Kidney Int. 1993; 43: 158-62

Two closely related secreted metalloproteases 72 and 92 kDa type IV collagenases (72- and 92T4Cl) consist of several structural domains, the functions of which are poorly understood. Both metalloproteases can bind to gelatin as well as form complexes with specific inhibitors in the proenzyme form. The biologic role of the proenzyme-inhibitor complex formation remained unclear. Here we summarize results demonstrating that the fibronectin-like domain of 92T4Cl mediates gelatin binding of the proenzyme, while the hemopexin like carboxy-terminal domain is essential for the complex formation of the proenzyme with TIMP. The formation of a 92T4Cl proenzyme complex with TIMP prevents dimerization, formation of the novel complex with ClI proenzyme, and activation of the 92T4Cl by stromelysin. Conversely, formation of the covalent 92T4Cl homodimer excludes the formation of a proenzyme-TIMP complex, thus allowing this form of enzyme to enter into the proteolytic cascade of activation. Both components of the 92T4Cl-ClI complex can be activated in a fashion similar to that of free enzymes, yielding a complex active against both gelatin and fibrillar collagen.

Specific collagenolysis by gelatinase A, MMP-2, is determined by the hemopexin domain and not the fibronectin-like domain.

Patterson ML, Atkinson SJ, Knauper V, Murphy G
FEBS Lett. 2001; 503: 158-62

In view of the essential role of the hemopexin domain of the traditional interstitial collagenases, MMP-1, -8, -13 and MT1-MMP (MMP-14), in determining specific collagen cleavage we have studied the function of this domain in MMP-2, relative to that of the fibronectin-like domain that promotes gelatinolysis. Although the fibronectin-like domain promotes avid binding to collagen, our data demonstrate that the catalytic and hemopexin domains of MMP-2 are sufficient to effect the critical step in cleavage of rat type I collagen into 3/4 and 1/4 fragments. The mechanism of MMP-2 cleavage of collagen proceeds in two phases, the first resembling that of the interstitial collagenases, followed by gelatinolysis, promoted by the fibronectin-like domain.

Identification of the TIMP-2 binding site on the gelatinase A hemopexin C-domain by site-directed mutagenesis and the yeast two-hybrid system.

Overall CM, King AE, Bigg HF, McQuibban A, Atherstone J, Sam DK, Ong AD, Lau TT, Wallon UM, DeClerck YA, Tam E
Ann N Y Acad Sci. 1999; 878: 747-53

Mechanisms for pro matrix metalloproteinase activation.

Murphy G, Stanton H, Cowell S, Butler G, Knauper V, Atkinson S, Gavrilovic J
APMIS. 1999; 107: 38-44

The activation of pro matrix metalloproteinases (MMPs) by sequential proteolysis of the propeptide blocking the active site cleft is regarded as one of the key levels of regulation of these proteinases. Potential physiological mechanisms including cell-associated plasmin generation by urokinase-like plasminogen activator, or the action of cell surface MT1-MMPs appear to be involved in the initiation of cascades of pro MMP activation. Gelatinase A, collagenase 3 and gelatinase B may be activated by MT-MMP based mechanisms, as evidenced by both biochemical and cell based studies. Hence the regulation of MT-MMPs themselves becomes critical to the determination of MMP activity. This includes activation, assembly at the cell surfaces as TIMP-2 complexes and subsequent inactivation by proteolysis or TIMP inhibition.

Activation of progelatinase B (proMMP-9) by active collagenase-3 (MMP-13).

Knauper V, Smith B, Lopez-Otin C, Murphy G
Eur J Biochem. 1997; 248: 369-73

Human progelatinase B was activated by collagenase-3 in a time-dependent fashion. Activation proceeded through an intermediate form of Mr 86,000 to the final active form of Mr 82,000. N-terminal amino acid sequence determination demonstrated that the Glu40-Met41 peptide bond was initially hydrolysed followed by cleavage of the Arg87-Phe88 peptide bond releasing the rest of the propeptide domain which was accompanied by the achievement of maximal enzymatic activity as revealed using a quenched fluorescent substrate. Kinetic analysis of activation revealed that the rates were dependent on the concentration of the proenzyme as well as active collagenase-3. Active gelatinase B did not contribute to the activation rate of the proenzyme initiated by collagenase-3 and our results indicate that progelatinase B activation proceeds via bimolecular cleavage with collagenase-3 involving sequential cleavage of the propeptide in two steps. The activation rates were not dependent on C-terminal domain interactions between progelatinase B and collagenase-3, as assessed using wild-type and C-terminal deletion mutants of both enzymes. Since elevated levels of both gelatinase B and collagenase-3 have been observed in arthritis and breast cancer pathology these enzymes may well form a proteolytic cascade in these diseases which allows rapid turnover of the extracellular matrix.

Plasma membrane-bound tissue inhibitor of metalloproteinases (TIMP)-2 specifically inhibits matrix metalloproteinase 2 (gelatinase A) activated on the cell surface.

Itoh Y, Ito A, Iwata K, Tanzawa K, Mori Y, Nagase H
J Biol Chem. 1998; 273: 24360-7

The cell-surface activation of pro-matrix metalloproteinase 2 (pro-MMP-2) is considered to be critical for cell migration and invasion. Treatment of human uterine cervical fibroblasts with concanavalin A activates pro-MMP-2 on the cell surface by converting it to the 65-kDa form with a minor form of 45 kDa. However, the 65-kDa MMP-2 was inactivated by tissue inhibitor of metalloproteinases (TIMP)-2 that was bound to the plasma membrane upon concanavalin A treatment. TIMP-2 binds to the plasma membrane through its N-terminal domain by two different modes of interaction as follows: one is sensitive to a hydroxamate (HXM) inhibitor of MMPs and the other is HXM-insensitive. TIMP-2 bound to the membrane in a HXM-insensitive manner, comprising about 40-50% of TIMP-2 on the membrane, is the inhibitor of the cell surface-activated MMP-2. It, however, does not inhibit MMP-3, MMP-9, and the 45-kDa MMP-2 lacking the C-terminal domain. The inhibition of the 65-kDa MMP-2 by TIMP-2 is initiated by the interaction of their C-terminal domains. Subsequently, the MMP-2.TIMP-2 complex is released from the membrane, and the activity of MMP-2 is blocked by TIMP-2. In the presence of collagen types I, II, III, V, or gelatin, the rate of inhibition of the 65-kDa MMP-2 by the membrane-bound TIMP-2 decreased considerably. These results suggest that the pericellular activity of MMP-2 is tightly regulated by membrane-bound TIMP-2 and surrounding extracellular matrix components.

Extracellular matrix-driven matrix metalloproteinase production in endothelial cells: implications for angiogenesis.

Haas TL, Madri JA
Trends Cardiovasc Med. 1999; 9: 70-7

The process of new blood vessel growth, angiogenesis, involves orchestrated alterations in endothelial cell interactions with adjacent cells and with components of the underlying basement membrane matrix. The activity of matrix metalloproteinases (MMPs), proteases that can cleave basement membrane and interstitial matrix molecules, has been shown to be necessary for angiogenesis as it occurs in several different in vivo and in vitro models. This review discusses the potential roles of two particular MMPs, MMP-2 and MT1-MMP, in angiogenesis, with emphasis on current understanding of how endothelial cell-extracellular matrix interactions may regulate the production of these MMPs via matrix-induced signaling leading to transcriptional activation and subsequent formation of active multiprotease complexes on the cell surface.

The C-terminal (haemopexin-like) domain structure of human gelatinase A (MMP2): structural implications for its function.

Gohlke U, Gomis-Ruth FX, Crabbe T, Murphy G, Docherty AJ, Bode W
FEBS Lett. 1996; 378: 126-30

In common with most other matrix metalloproteinases, gelatinase A has a non-catalytic C-terminal domain that displays sequence homology to haemopexin. Crystals of this domain were used by molecular replacement to solve its molecular structure at 2.6 A resolution, which was refined to an R value of 17.9%. This structure has a disc-like shape, with the chain folded into a beta-propeller structure that has pseudo four-fold symmetry. Although the topology and the side-chain arrangement are very similar to the equivalent domain of fibroblast collagenase, significant differences in surface charge and contouring are observable on 1 side of the gelatinase A disc. This difference might be a factor in allowing the gelatinase A C-terminal domain to bind to natural inhibitor TIMP-2.

Crystal structure of the complex formed by the membrane type 1-matrix metalloproteinase with the tissue inhibitor of metalloproteinases-2, the soluble progelatinase A receptor.

Fernandez-Catalan C, Bode W, Huber R, Turk D, Calvete JJ, Lichte A, Tschesche H, Maskos K
EMBO J. 1998; 17: 5238-48

The proteolytic activity of matrix metalloproteinases (MMPs) towards extracellular matrix components is held in check by the tissue inhibitors of metalloproteinases (TIMPs). The binary complex of TIMP-2 and membrane-type-1 MMP (MT1-MMP) forms a cell surface located 'receptor' involved in pro-MMP-2 activation. We have solved the 2.75 A crystal structure of the complex between the catalytic domain of human MT1-MMP (cdMT1-MMP) and bovine TIMP-2. In comparison with our previously determined MMP-3-TIMP-1 complex, both proteins are considerably tilted to one another and show new features. CdMT1-MMP, apart from exhibiting the classical MMP fold, displays two large insertions remote from the active-site cleft that might be important for interaction with macromolecular substrates. The TIMP-2 polypeptide chain, as in TIMP-1, folds into a continuous wedge; the A-B edge loop is much more elongated and tilted, however, wrapping around the S-loop and the beta-sheet rim of the MT1-MMP. In addition, both C-terminal edge loops make more interactions with the target enzyme. The C-terminal acidic tail of TIMP-2 is disordered but might adopt a defined structure upon binding to pro-MMP-2; the Ser2 side-chain of TIMP-2 extends into the voluminous S1' specificity pocket of cdMT1-MMP, with its Ogamma pointing towards the carboxylate of the catalytic Glu240. The lower affinity of TIMP-1 for MT1-MMP compared with TIMP-2 might be explained by a reduced number of favourable interactions.

Tissue inhibitor of metalloproteinase-2 protection of matrix metalloproteinase-2 from degradation by plasmin is reversed by divalent cation chelator EDTA and the bisphosphonate alendronate.

Farina AR, Tacconelli A, Teti A, Gulino A, Mackay AR
Cancer Res. 1998; 58: 2957-60

The degradation of tissue inhibitor of metalloproteinase (TIMP)-free matrix metalloproteinase (MMP)-2 to proteolytically inactive fragments by plasmin was inhibited in equimolar mixtures of purified TIMP-2 and TIMP-free MMP-2 and was not observed in purified MMP-2-TIMP-2 complexes. Divalent cation chelators EDTA and sodium Alendronate did not inhibit plasmin degradation of TIMP-free MMP-2 but reversed the ability of TIMP-2 to protect MMP-2 from degradation by plasmin. Our data confirm a role for plasmin in the clearance of TIMP-free MMP-2, identify a pivotal role for TIMP-2 in regulating MMP-2 longevity in plasmin-containing environments, and highlight a novel therapeutic use for chelators of divalent cations, including the bisphosphonate Alendronate, in the reversal of TIMP-2 protection of MMP-2 from degradation by plasmin. We propose that these observations are relevant to pathologies that are dependent upon plasmin and MMP-2 activity (e.g., tumor invasion and metastasis).

Remodeling of collagen matrix by human tumor cells requires activation and cell surface association of matrix metalloproteinase-2.

Deryugina EI, Bourdon MA, Reisfeld RA, Strongin A
Cancer Res. 1998; 58: 3743-50

We assessed the functional significance of tumor cell-associated matrix metalloproteinase (MMP)-2 in extracellular matrix remodeling compared with that of the soluble enzyme by evaluating the contraction of three-dimensional collagen lattices by human glioma U251.3 and fibrosarcoma HT-1080 cell lines. In this model, the constitutive synthesis and activation of the MMP-2 proenzyme were modulated by stable transfections of tumor cells with cDNA encoding membrane type 1-MMP (MT1-MMP). The efficiency of transfected cells in contracting collagen lattices was shown to be dependent on the MT1-MMP-mediated activation of MMP-2 accompanied by cell surface association of activated MMP-2, on the cell-matrix interactions controlled by collagen-specific integrins, and on the integrity of actin and microtubule cytoskeletons. Each one of these mechanisms was essential but was not sufficient by itself in accomplishing gel contraction by MT1-MMP-transfected cells. Both MMP-2 activation and gel contraction by transfected glioma cells were inhibited by tissue inhibitor of metalloproteinase (TIMP)-2 and the recombinant COOH-terminal domain of MMP-2. However, the kinetics and mechanisms of their inhibitory effects were different, because TIMP-2 and the COOH-terminal domain of MMP-2 preferentially inhibited the MT1-MMP-dependent and autocatalytic steps of MMP-2 activation, respectively. By contrast, TIMP-1, an efficient inhibitor of soluble MMP-2 activity, failed to affect gel contraction. In addition, soluble MMP-2 activated by either organomercurials or cells was not able to induce the contraction of collagen lattices when added to transfected cells. Therefore, soluble activated MMP-2, sensitive to TIMP-1 inhibition, does not mediate collagen gel contraction by tumor cells, whereas the activity of cell surface-associated MMP-2 plays a critical role in remodeling of the extracellular matrix in vitro. These mechanisms of functional and spatial regulation of MMP-2 may also be applicable to different aspects of tissue reorganization in vivo, including cell migration and invasion, angiogenesis, and wound healing.

Expression and activation of pro-gelatinase A by human melanoma cell lines with different tumorigenic potential.

Capon F, Emonard H, Hornebeck W, Maquart FX, Bernard P
Clin Exp Metastasis. 1999; 17: 463-9

The production of various proteolytic enzymes by tumor cells facilitate the invasion of solid tumors into surrounding tissues. We examined three cell lines (M1Dor, M4Be and M3Da) derived from malignant melanoma which exhibited different abilities to grow in nude mice following subcutaneous grafting. By in vitro invasion assay using Boyden-chambers technique, we found that none of those cell lines were able to invade the Matrigel. Several studies have substantiated the role of matrix metalloproteinases (MMP), mainly gelatinases MMP-9 and MMP-2, in melanoma cell invasion. Each cell line constitutively produced MMP-2 (but not MMP-9) in its latent form only, with stronger production for the most tumorigenic cell line in vivo (M3Da). Integrity of the MMP-2 activation process was studied since MMP-2 was also recovered as zymogen at the cell plasma membrane. All cell lines secreted TIMP-1 and TIMP-2 in a constitutive manner and again, but TIMP-2 production as well as MT1-MMP expression were found inversely related to their tumorigenic potential. Plating cells onto type I or type IV collagen did not trigger pro-MMP-2 activation; on the contrary, conversion of pro-MMP-2 to its active form could be evidenced when melanoma cell lines were seeded in a three dimensional type I collagen lattice.

The specificity of TIMP-2 for matrix metalloproteinases can be modified by single amino acid mutations.

Butler GS, Hutton M, Wattam BA, Williamson RA, Knauper V, Willenbrock F, Murphy G
J Biol Chem. 1999; 274: 20391-6

Residues 1-127 of human TIMP-2 (N-TIMP-2), comprising three of the disulfide-bonded loops of the TIMP-2 molecule, is a discrete protein domain that folds independently of the C-terminal domain. This domain has been shown to be necessary and sufficient for metalloproteinase inhibition and contains the major sites of interaction with the catalytic N-terminal domain of active matrix metalloproteinases (MMPs). Residues identified as being involved in the interaction with MMPs by NMR chemical shift perturbation studies and TIMP/MMP crystal structures have been altered by site-directed mutagenesis. We show, by measurement of association rates and apparent inhibition constants, that the specificity of these N-TIMP-2 mutants for a range of MMPs can be altered by single site mutations in either the TIMP "ridge" (Cys1-Cys3 and Ser68-Cys72) or the flexible AB loop (Ser31-Ile41). This work demonstrates that it is possible to engineer TIMPs with altered specificity and suggests that this form of protein engineering may be useful in the treatment of diseases such as arthritis and cancer where the selective inhibition of key MMPs is desirable.

Human tissue inhibitor of metalloproteinases 3 interacts with both the N- and C-terminal domains of gelatinases A and B. Regulation by polyanions.

Butler GS, Apte SS, Willenbrock F, Murphy G
J Biol Chem. 1999; 274: 10846-51

We compared the association constants of tissue inhibitor of metalloproteinases (TIMP)-3 with various matrix metalloproteinases with those for TIMP-1 and TIMP-2 using a continuous assay. TIMP-3 behaved more like TIMP-2 than TIMP-1, showing rapid association with gelatinases A and B. Experiments with the N-terminal domain of gelatinase A, the isolated C-terminal domain, or an inactive progelatinase A mutant showed that the hemopexin domain of gelatinase A makes an important contribution to the interaction with TIMP-3. The exchange of portions of the gelatinase A hemopexin domain with that of stromelysin revealed that residues 568-631 of gelatinase A were required for rapid association with TIMP-3. The N-terminal domain of gelatinase B alone also showed slower association with TIMP-3, again implying significant C-domain interactions. The isolation of complexes between TIMP-3 and progelatinases A and B on gelatin-agarose demonstrated that TIMP-3 binds to both proenzymes. We analyzed the effect of various polyanions on the inhibitory activity of TIMP-3 in our soluble assay. The association rate was increased by dextran sulfate, heparin, and heparan sulfate, but not by dermatan sulfate or hyaluronic acid. Because TIMP-3 is sequestered in the extracellular matrix, the presence of certain heparan sulfate proteoglycans could enhance its inhibitory capacity.

Tissue inhibitors of metalloproteinases: evolution, structure and function.

Brew K, Dinakarpandian D, Nagase H
Biochim Biophys Acta. 2000; 1477: 267-83

The matrix metalloproteinases (MMPs) play a key role in the normal physiology of connective tissue during development, morphogenesis and wound healing, but their unregulated activity has been implicated in numerous disease processes including arthritis, tumor cell metastasis and atherosclerosis. An important mechanism for the regulation of the activity of MMPs is via binding to a family of homologous proteins referred to as the tissue inhibitors of metalloproteinases (TIMP-1 to TIMP-4). The two-domain TIMPs are of relatively small size, yet have been found to exhibit several biochemical and physiological/biological functions, including inhibition of active MMPs, proMMP activation, cell growth promotion, matrix binding, inhibition of angiogenesis and the induction of apoptosis. Mutations in TIMP-3 are the cause of Sorsby's fundus dystrophy in humans, a disease that results in early onset macular degeneration. This review highlights the evolution of TIMPs, the recently elucidated high-resolution structures of TIMPs and their complexes with metalloproteinases, and the results of mutational and other studies of structure-function relationships that have enhanced our understanding of the mechanism and specificity of the inhibition of MMPs by TIMPs. Several intriguing questions, such as the basis of the multiple biological functions of TIMPs, the kinetics of TIMP-MMP interactions and the differences in binding in some TIMP-metalloproteinase pairs are discussed which, though not fully resolved, serve to illustrate the kind of issues that are important for a full understanding of the interactions between families of molecules.

Structure of recombinant mouse collagenase-3 (MMP-13).

Botos I, Meyer E, Swanson SM, Lemaitre V, Eeckhout Y, Meyer EF
J Mol Biol. 1999; 292: 837-44

The matrix metalloproteinases are crucial in the physiological and pathological degradation of the mammalian extracellular matrix, including breast tumours, and osteoarthritic cartilage. These enzymes are classified according to their matrix substrate specificity. Collagenase-3 (MMP-13) is a member of this family and preferentially cleaves type II collagen, cartilage, fibronectin and aggrecan. Collagenase-3 is normally expressed in hypertrophic chondrocytes, periosteal cells, and osteoblasts during bone development. The structure of the catalytic domain of recombinant mouse collagenase-3, complexed to the hydroxamate inhibitor (RS-113456), is reported at 2.0 A resolution. Molecular replacement and weak phasing information from a single derivative determined the structure. Neither molecular replacement nor derivative methods had a sufficient radius of convergence to yield a refinable structure. The structure illuminates the atomic zinc ion interactions with functional groups in the active site, emphasizing zinc ligation and the very voluminous hydrophobic P1' group for the inhibitor potency. The structure provides insight into the specificity of this enzyme, facilitating design of specific inhibitors to target various diseases.

Insights into MMP-TIMP interactions.

Bode W, Fernandez-Catalan C, Grams F, Gomis-Ruth FX, Nagase H, Tschesche H, Maskos K
Ann N Y Acad Sci. 1999; 878: 73-91

The proteolytic activity of the matrix metalloproteinases (MMPs) involved in extracellular matrix degradation must be precisely regulated by their endogenous protein inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Disruption of this balance can result in serious diseases such as arthritis and tumor growth and metastasis. Knowledge of the tertiary structures of the proteins involved in such processes is crucial for understanding their functional properties and to interfere with associated dysfunctions. Within the last few years, several three-dimensional structures have been determined showing the domain organization, the polypeptide fold, and the main specificity determinants of the MMPs. Complexes of the catalytic MMP domains with various synthetic inhibitors enabled the structure-based design and improvement of high-affinity ligands, which might be elaborated into drugs. Very recently, structural information also became available for some TIMP structures and MMP-TIMP complexes, and these new data elucidated important structural features that govern the enzyme-inhibitor interaction.

A helping hand for collagenases: the haemopexin-like domain.

Bode W
Structure. 1995; 3: 527-30

The structures of the C-terminal domains of rabbit haemopexin and full-length porcine fibroblast collagenase reveal a common beta-propeller fold with pseudo-fourfold symmetry. The interactions of these haemopexin-like domains with target proteins and ligands is, however, still a matter of debate.

Structure and domain-domain interactions of the gelatin binding site of human 72-kilodalton type IV collagenase (gelatinase A, matrix metalloproteinase 2).

Banyai L, Tordai H, Patthty L
J Biol Chem. 1996; 271: 12003-8

We have shown previously that all three fibronectin type II modules of gelatinase A contribute to its gelatin affinity. In the present investigation we have studied the structure and module-module interactions of this gelatin-binding domain by circular dichroism spectroscopy and differential scanning calorimetry. Comparison of the Tm values of the thermal transitions of isolated type II modules with those of bimodular or trimodular proteins has shown that the second type II module is significantly more stable in the trimodular protein coll 123 (Tm = 54 degrees C) than in the single-module protein coll 2 (Tm = 44 degrees C) or in the bimodular proteins coll 23 (Tm = 47 degrees C) and coll 12 (Tm = 48 degrees C). Analysis of the enthalpy changes associated with thermal unfolding of the second type II module suggests that it is stabilized by domain-domain interactions in coll 123. We propose that intimate contacts exist between the three tandem type 11 units and they form a single gelatin-binding site. Based on the three-dimensional structures of homologous metalloproteases and type II modules, a model is proposed in which the three type II units form an extension of the substrate binding cleft of gelatinase A.