Transglutaminase diseases: from biochemistry to the bedside.

In humans, 9 members of the transglutaminase (TG) family have been identified, of which 8 [factor XIII (FXIII)A and TG1-TG7] catalyze post-translational protein-modifying reactions, and 1 does not (protein 4.2). The TG enzymatic activities considered in our discussion of human disease include deamidation of glutamine (Gln) residues, amine incorporation into Gln residues, and protein crosslinking.

Transglutaminase 2 is essential for adherence of Porphyromonas gingivalis to host cells.

Porphyromonas gingivalis is the major causative agent of periodontitis, and it may also be involved in the development of systemic diseases (atherosclerosis, rheumatoid arthritis). P. gingivalis is found on and within oral and gingival epithelial cells following binding to surface components of host cells, which serve as receptors for the bacterium.

Transglutaminases and disease: lessons from genetically engineered mouse models and inherited disorders.

The human transglutaminase (TG) family consists of a structural protein, protein 4.2, that lacks catalytic activity, and eight zymogens/enzymes, designated factor XIII-A (FXIII-A) and TG1-7, that catalyze three types of posttranslational modification reactions: transamidation, esterification, and hydrolysis. These reactions are essential for biological processes such as blood coagulation, skin barrier formation, and extracellular matrix assembly but can also contribute to the pathophysiology of various inflammatory, autoimmune, and degenerative conditions.

Selectivity in the post-translational, transglutaminase-dependent acylation of lysine residues.

Transglutaminases (TGs) are known to exhibit remarkable specificities not only for the Q (or Gln) sites but also for the K (or Lys) sites of proteins with which they react. To gain further insight into K-site specificity, we examined the reactions of dansyl-epsilon-aminocaproyl-GlnGlnIleVal with three chemically and structurally well-characterized proteins (bovine pancreatic ribonuclease A, bovine pancreatic trypsin inhibitor, and chicken egg white lysozyme), as catalyzed by TG2, a biologically important post-translational enzyme. The substrates represent a total of 20 potential surface sites for acylation by the fluorescent Gln probe, yet only two of the lysine side chains reacted with TG2.

Micromechanical properties of keratin intermediate filament networks.

Keratin intermediate filaments (KIFs) form cytoskeletal KIF networks that are essential for the structural integrity of epithelial cells. However, the mechanical properties of the in situ network have not been defined. Particle-tracking microrheology (PTM) was used to obtain the micromechanical properties of the KIF network in alveolar epithelial cells (AECs), independent of other cytoskeletal components, such as microtubules and microfilaments.

Mechanism of allosteric regulation of transglutaminase 2 by GTP.

Allosteric regulation is a fundamental mechanism of biological control. Here, we investigated the allosteric mechanism by which GTP inhibits cross-linking activity of transglutaminase 2 (TG2), a multifunctional protein, with postulated roles in receptor signaling, extracellular matrix assembly, and apoptosis. Our findings indicate that at least two components are involved in functionally coupling the allosteric site and active center of TG2, namely (i) GTP binding to mask a conformationally destabilizing switch residue, Arg-579, and to facilitate interdomain interactions that promote adoption of a compact, catalytically inactive conformation and (ii) stabilization of the inactive conformation by an uncommon H bond between a cysteine (Cys-277, an active center residue) and a tyrosine (Tyr-516, a residue located on a loop of the beta-barrel 1 domain that harbors the GTP-binding site).

Endomysial antibody-negative coeliac disease: clinical characteristics and intestinal autoantibody deposits.

Background: Some patients with untreated coeliac disease are negative for serum endomysial autoantibodies (EmA) targeted against transglutaminase 2 (TG2).

Aims: To evaluate the clinical and histological features of EmA-negative coeliac disease, and to examine whether EmA-equivalent autoantibodies against TG2 can be seen in the small-bowel mucosa when absent in serum.

Patients: Serum EmA was studied in 177 biopsy-proved specimens from adult patients with coeliac disease.

Identification of a novel recognition sequence for fibronectin within the NH2-terminal beta-sandwich domain of tissue transglutaminase.

Tissue transglutaminase belongs to the multigene transglutaminase family of Ca2+-dependent protein cross-linking enzymes. Unlike other transglutaminases, it is involved in cell-matrix interactions and serves as an adhesion co-receptor for fibronectin. Previous work established that the fibronectin-binding motif(s) is located within the NH2-terminal proteolytic fragment of the protein consisting of residues 1-272.

Deciphering the physiological pathway of clotting of fibrinogen in blood plasma.

I have been fortunate to have benefited over the years from the friendship and advice of John Ferry in our research to decipher the physiological reactions and regulatory events involved in the clotting of fibrinogen in blood. The article is a tribute to the memory of this creative scientist and remarkable individual.

Severe hypodysfibrinogenemia in compound heterozygotes of the fibrinogen AalphaIVS4 + 1G>T mutation and an AalphaGln328 truncation (fibrinogen Keokuk).

Two siblings with hypofibrinogenemia have lifelong trauma-related bleeding. Recently, the brother experienced recurrent thrombosis after cryoprecipitate infusions following surgery. The sister had 6 miscarriages.

Evolutionary specialization of a tryptophan indole group for transition-state stabilization by eukaryotic transglutaminases.

Covalent posttranslational protein modifications by eukaryotic transglutaminases proceed by a kinetic pathway of acylation and deacylation. Ammonia is released as the acylenzyme is formed, whereas the cross-linked product is released later in the deacylation step. Superposition of the active sites of transglutaminase type 2 (TG2) and the structurally related cysteine protease, papain, indicates that in the formation of tetrahedral intermediates, the backbone nitrogen of the catalytic Cys-277 and the N1 nitrogen of Trp-241 of TG2 could contribute to transition-state stabilization.

Activation of transglutaminase in mu-calpain null erythrocytes.

Intracellular transglutaminases (protein-glutamine: amine gamma-glutamyltransferase, EC 2.3.2.

Transglutaminases: crosslinking enzymes with pleiotropic functions.

Blood coagulation, skin-barrier formation, hardening of the fertilization envelope, extracellular-matrix assembly and other important biological processes are dependent on the rapid generation of covalent crosslinks between proteins. These reactions--which are catalysed by transglutaminases--endow the resulting supramolecular structure with extra rigidity and resistance against proteolytic degradation. Some transglutaminases function as molecular switches in cytoskeletal scaffolding and modulate protein-protein interactions.

Intracranial hemorrhage in systemic lupus erythematosus associated with an autoantibody against actor XIII.

Intracranial hemorrhage in a young woman with systemic lupus erythematosus necessitated two surgical evacuations. In the absence of a family history of bleeding, clot solubility in urea suggested a factor XIII (FXIII) inhibitor. The patient's IgG bound well to the virgin and the thrombin-modified zymogen ensemble (A(2)B(2) and A(2)'B(2)) and to the free rA(2) but reacted poorly with the thrombin-modified rA(2)'.

Conserved tryptophan in the core domain of transglutaminase is essential for catalytic activity.

Transglutaminase 2 (TG2) is a distinctive member of the family of Ca2+-dependent enzymes recognized mostly by their abilities to catalyze the posttranslational crosslinking of proteins. TG2 uniquely binds and hydrolyzes GTP; binding GTP inhibits its crosslinking activity but allows it to function in signal transduction (hence the G(h) designation). The core domain of TG2 (residues 139-471, rat) comprises the papain-like catalytic triad and the GTP-binding domain (residues 159-173) and contains almost all of the conserved tryptophans of the protein.

Factor XIII: structure, activation, and interactions with fibrinogen and fibrin.

Fibrin stabilizing factor (factor XIII or FXIII) plays a critical role in the generation of a viable hemostatic plug. Following exposure to thrombin and calcium, the zymogen is activated to FXIIIa that, in turn, catalyzes the formation of N epsilon(gamma-glutamyl)lysine protein-to-protein side chain bridges within the clot network. Introduction of these covalent crosslinks greatly augments the viscoelastic storage modulus of the structure and its resistance to fibrinolytic enzymes.

[Effect of portal branch ligation on liver regeneration in the rat].

Goal: The aim of this study was to assess liver regeneration after partial portal ligation.

Methods: 70% partial portal occlusion was obtained by ligation of the left portal vein branch. Total liver weight ratio were measured 96 hours after partial portal occlusion and in sham operated animals.

Nucleotide binding by the erythrocyte transglutaminase/Gh protein, probed with fluorescent analogs of GTP and GDP.

GTP is known to be a potent inhibitor of the protein crosslinking activity of transglutaminase (TG), probably the most abundant G protein in the human red cell. Nucleotide binding to TG was examined by fluorescence spectroscopy and anisotropy in mixtures of TG with methylanthraniloyl analogs of GTP and GDP. A characteristic feature was the appearance of a major energy transfer band (lambda(exc, max) = 290 nm, lambda(em) = 444 nm) from protein tryptophans to the bound nucleotides.

Covalent cross-linking of secreted bovine thyroglobulin by transglutaminase.

Extracellular storage of thyroglobulin (TG) is a prerequisite for maintaining constant levels of thyroid hormones in vertebrates. Storage of TG within the follicle lumen is achieved by compactation and by the formation of covalent cross-links between TG molecules. In bovine thyroids, approximately 75% of the cross-links are other than disulfide bonds (J.