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‣ Affinity of human erythrocyte transglutaminase for a 42-kDa gelatin-binding fragment of human plasma fibronectin.

Radek, J T; Jeong, J M; Murthy, S N; Ingham, K C; Lorand, L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/04/1993 Português
Relevância na Pesquisa
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Complex formation between the human erythrocyte transglutaminase (protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13) and fibronectin or its fragments was examined by immunoanalytical procedures and by fluorescence polarization. A 42-kDa gelatin-binding structure, obtained from human plasma fibronectin by thermolytic digestion, showed as high an affinity for the cytosolic enzyme as the parent fibronectin chains themselves. A 21-kDa fragment comprising type I modules 8 and 9, the last two modules in the 42-kDa fragment, bound with an affinity 100-fold less than the 42-kDa fragment. Binding was remarkably specific and could be exploited for the affinity purification of transglutaminase directly from the hemoglobin-depleted erythrocyte lysate. In spite of the high affinity, it was possible to elute active enzyme from the 42-kDa fragment column with 0.25% monochloroacetic acid. This solvent might have general applicability in other systems involving separation of tightly bound ligands.

‣ Organization and evolution of the human epidermal keratinocyte transglutaminase I gene.

Polakowska, R R; Eickbush, T; Falciano, V; Razvi, F; Goldsmith, L A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/05/1992 Português
Relevância na Pesquisa
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Transglutaminases (TGases; protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13) are calcium-dependent crosslinking enzymes that modify proteins posttranslationally. Several distinct types of TGases have been identified, which appear to be encoded by a family of closely related genes. We isolated the gene encoding human keratinocyte-specific type I TGase (TGase I) and characterized its chromosomal organization. The TGase I gene consists of 15 exons separated by 14 introns and exhibits a restriction fragment length polymorphism. Exons appear to encode functional and/or structural domains: exon I and part of exon XV encode untranslated regions, whereas exons VII and XI contain the active site and a presumptive calcium-binding domain, respectively. Interestingly, exon VI of TGase I contains a consensus Arg-Gly-Asp tripeptide sequence whose presence suggests an intriguing extracellular function for the enzyme. We present a likely phylogenetic tree for seven known members of the TGase family based on amino acid sequence similarity. Arguments presented suggest that the active enzyme evolved first and the structural human erythrocyte membrane protein 4.2 (band 4.2) has undergone a rapid change in amino acid sequence. It follows that band 4.2 evolved from the type II TGases...

‣ Isolation of transglutaminase-reactive sequences from complex biological systems: a prominent lysine donor sequence in bovine lens.

Lorand, L; Velasco, P T; Murthy, S N; Wilson, J; Parameswaran, K N
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/1992 Português
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The transglutaminase (protein-glutamine: amine gamma-glutamyltransferase, EC 2.3.2.13)-catalyzed cross-linking of proteins in biological systems can often be inhibited by inclusion of small primary amines or glutamine-containing peptides, which act as site-specific blockers of the relevant acceptor (i.e., glutamine) and donor (i.e., lysine) functionalities of the natural substrates. Compounds such as dansylcadaverine and dansyl-epsilon-aminocaproyl-Gln-Gln-Ile-Val are particularly useful in sorting out acceptor-donor relationships among lens crystallins. Apart from its fluorescent properties, the dansyl hapten offered special advantages as a "handle" for the rapid isolation of transglutaminase targets even in the complex system of lens cortical homogenate. The dansylated peptide was incorporated into bovine lens proteins under the influence of the Ca(2+)-activated intrinsic transglutaminase and, after digestion by endoproteinase Glu-C, the tracer-containing fragments were isolated by affinity chromatography on an anti-dansyl antibody column. The major fluorescent peak was isolated by HPLC and sequenced by Edman degradation, which yielded phenylthiohydantoin amino acid derivatives for the first 10 cycles, EKPAVTAAPK, and none for the next 2. The sequence...

‣ Sorting-out of acceptor-donor relationships in the transglutaminase-catalyzed cross-linking of crystallins by the enzyme-directed labeling of potential sites.

Lorand, L; Parameswaran, K N; Velasco, P T
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/01/1991 Português
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The dansyl-conjugated (Dns) peptides Dns-Pro-Gly-Gly-Gln-Gln-Ile-Val and Dns-Ala-Gln-Gln-Ile-Val, patterned on the N-terminal sequence of fibronectin, were synthesized and used for the transglutaminase (protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13)-directed selective blocking of lens proteins that otherwise might participate in donating lysyl side chains in forming N epsilon-(gamma-glutamyl)-lysine cross-linked oligomers and polymers. Labeling profiles with these peptides could be readily visualized by fluorescence as well as by immunoblotting with anti-dansyl antibody. The labeling patterns in rabbit lens homogenates were quite different with the dansylated peptides than those obtained with dansylcadaverine. Use of such glutamine-containing dansylated peptides should clearly aid in identifying, isolating, and sequencing potential donor substrates of transglutaminases in many biological systems.

‣ Intramolecular crosslinking of monomeric fibrinogen by tissue transglutaminase.

Murthy, S N; Wilson, J; Guy, S L; Lorand, L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/1991 Português
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In addition to generating polymeric products from human fibrinogen, human erythrocyte transglutaminase (protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13) was shown to catalyze the intramolecular reaction of crosslinking two of the constituent chains within monomeric fibrinogen itself. This internally fused protein derivative contains appreciable amounts of the N epsilon-(gamma-glutamyl)lysine bridge peptide and displays the A alpha.gamma hybrid chain pattern of crosslinking, characteristic for the actions of tissue transglutaminases on fibrinogen. Diagnostic analysis in pathological situations, where such enzymes might have escaped from cells into the plasma environment, should include a search for the internally crosslinked soluble fibrinogen monomer.

‣ Complete amino acid sequence and homologies of human erythrocyte membrane protein band 4.2.

Korsgren, C; Lawler, J; Lambert, S; Speicher, D; Cohen, C M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1990 Português
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The complete amino acid sequence for human erythrocyte band 4.2 has been derived from the nucleotide sequence of a full-length 2.35-kilobase (kb) cDNA. The 2.35-kb cDNA was isolated from a human reticulocyte cDNA library made in the expression vector lambda gt11. Of the 2348 base pairs (bp), 2073 bp encode 691 amino acids representing 76.9 kDa (the SDS/PAGE molecular mass is 72 kDa). RNA blot analysis of human reticulocyte total RNA gives a message size for band 4.2 of 2.4 kb. The amino acid sequence of band 4.2 has homology with two closely related Ca2(+)-dependent cross-linking proteins, guinea pig liver transglutaminase (protein-glutamine gamma-glutamyltransferase; protein-glutamine: amine gamma-glutamyltransferase, EC 2.3.2.13) (32% identity in a 446-amino acid overlap) and the a subunit of human coagulation factor XIII (27% identity in a 639-amino acid overlap), a transglutaminase that forms intermolecular gamma-glutamyl-epsilon-lysine bonds between fibrin molecules. The region of greatest identity includes a 49-amino acid stretch of band 4.2, which is 69% and 51% identical with guinea pig liver transglutaminase and the a subunit of factor XIII, respectively, within the regions that contain the active sites of these enzymes. Significantly...

‣ Labeling of epsilon-lysine crosslinking sites in proteins with peptide substrates of factor XIIIa and transglutaminase.

Parameswaran, K N; Velasco, P T; Wilson, J; Lorand, L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1990 Português
Relevância na Pesquisa
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Peptides patterned on the N-terminal sequence of fibronectin were synthesized and tested for amine acceptor qualities in reactions with dansylcadaverine catalyzed either by coagulation factor XIIIa or intracellular transglutaminase (protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13). On the basis of inverse half-saturations of the enzymes, the order of acceptor substrate affinity for factor XIIIa was pEAQQIV much greater than Boc-AQQIV greater than Boc-QQIV, and for transglutaminase, Boc-QQIV greater than Boc-AQQIV greater than pEAQQIV (amino acid residues are shown in one-letter code; pE, pyroglutamic acid; Boc, tert-butyloxycarbonyl). Sequence analysis of dansylcadaverine-substituted pEAQQIV indicated that the first of the two adjacent glutamine residues was the target of enzymatic modification. Boc-QIV showed no substrate activity with either enzyme. Crosslinking of crystallins in Ca2(+)-treated rabbit lens homogenate was readily inhibited by Boc-QQIV, Boc-AQQIV, and pEAQQIV, as was the formation of alpha-chain polymers in human fibrin by pEAQQIV in the presence of human factor XIIIa. SDS/PAGE analysis suggested that the inhibitory peptides selectively blocked the electron donor functionalities in these enzymatic crosslinking reactions.

‣ Primary structure of keratinocyte transglutaminase.

Phillips, M A; Stewart, B E; Qin, Q; Chakravarty, R; Floyd, E E; Jetten, A M; Rice, R H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1990 Português
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The nucleotide and deduced amino acid sequences of the coding regions of human and rat keratinocyte transglutaminases (protein-glutamine: amine gamma-glutamyltransferase; EC 2.3.2.13) have been determined. These yield proteins of approximately 90 kDa that are 92% identical, indicative of the conservation of important structural features. Alignments of amino acid sequences show substantial similarity among the keratinocyte transglutaminase, human clotting factor XIII catalytic subunit, guinea pig liver tissue transglutaminase, and the human erythrocyte band-4.2 protein. The keratinocyte enzyme is most similar to factor XIII, whereas the band-4.2 protein is most similar to the tissue transglutaminase. A salient feature of the keratinocyte transglutaminase is its 105-residue extension beyond the N terminus of the tissue transglutaminase. This extension and the unrelated activation peptide of factor XIII (a 37-residue extension) appear to be added for specialized functions after divergence of the tissue transglutaminase from their common lineage.

‣ Overexpression of a Streptomyces viridochromogenes gene (glnII) encoding a glutamine synthetase similar to those of eucaryotes confers resistance against the antibiotic phosphinothricyl-alanyl-alanine.

Behrmann, I; Hillemann, D; Pühler, A; Strauch, E; Wohlleben, W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1990 Português
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Phosphinothricyl-alanyl-alanine (PTT), also known as bialaphos, contains phosphinothricin, a potent inhibitor of glutamine synthetase (GS). A 2.75-kilobase NcoI fragment of the Streptomyces viridochromogenes PTT-resistant mutant ES2 cloned on a multicopy vector mediated PTT resistance to S. lividans and to S. viridochromogenes. Nucleotide sequence analysis of the 2.75-kb NcoI fragment revealed the presence of three open reading frames. Open reading frame 3 was termed glnII since significant similarity was found between its deduced amino acid sequence and those from GS of eucaryotes and GSII of members of the family Rhizobiaceae. Subcloning experiments showed that PTT resistance is mediated by overexpression of glnII encoding a 37.3-kilodalton protein of 343 amino acids. A three- to fourfold increase in gamma-glutamyltransferase activity could be observed in S. lividans transformants carrying the glnII gene on a multicopy plasmid. For S. viridochromogenes it was shown that PTT resistance conferred by the 2.75-kb NcoI fragment was dependent on its multicopy state. GS activity encoded by glnII was found to be heat labile. Southern hybridization with seven different Streptomyces strains suggested that they all carry two types of GS genes...

‣ Fibronectin as a carrier for the transglutaminase from human erythrocytes.

Lorand, L; Dailey, J E; Turner, P M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1988 Português
Relevância na Pesquisa
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Nondenaturing electrophoresis was used to demonstrate that, immediately upon exposure to plasma, the transglutaminase (protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13) from erythrocytes undergoes a significant shift in mobility. The plasma effect shows saturable characteristics and depends entirely on the presence of fibronectin in plasma, indicative of complex formation between this protein and transglutaminase. The results suggest a specific carrier function for fibronectin that might be of physiological importance in determining the fate of a tissue transglutaminase accidentally discharged into plasma.

‣ Regulation of glutamine synthetase activity by adenylylation in the Gram-positive bacterium Streptomyces cattleya.

Streicher, S L; Tyler, B
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1981 Português
Relevância na Pesquisa
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The enzymatic activity of glutamine synthetase [GS; L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] from the Gram-positive bacterium Streptomyces cattleya is regulated by covalent modification. In whole cells containing high levels of GS the addition of ammonium chloride leads to a rapid decline in GS activity. Crude extracts prepared from such ammonia-shocked cells had very low levels of GS activity as measured by biosynthetic and gamma-glutamyltransferase assays. Incubation of the crude extracts with snake venom phosphodiesterase restored GS activity. In cell extracts, GS was also inactivated by an ATP- and glutamine-dependent reaction. Radioactive labeling studies demonstrated the incorporation of an AmP moiety into GS protein upon modification. Our results suggest a covalent modification of GS in a Gram-positive bacterium. This modification appears to be adenylylation of the GS subunit similar to that found in the Gram-negative bacteria.

‣ Primary structure of blood coagulation factor XIIIa (fibrinoligase, transglutaminase) from human placenta.

Takahashi, N; Takahashi, Y; Putnam, F W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1986 Português
Relevância na Pesquisa
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We have determined the primary structure of human placental factor XIIIa, an enzyme [fibrinoligase, transglutaminase, fibrin-stabilizing factor, EC 2.3.2.13 (protein-glutamine:amine gamma-glutamyltransferase)] that forms intermolecular isopeptide bonds between fibrin molecules as the last step in blood coagulation. Placental factor XIIIa is an unglycosylated polypeptide chain of 730 amino acid residues (Mr = 83,005) that appears to be identical to the a subunit of the plasma zymogen factor XIII. Ca2+-dependent activation of factor XIIIa by thrombin removes a blocked amino-terminal peptide and unmasks a reactive thiol group at Cys-314. A second specific cleavage after Lys-513 by thrombin inactivates factor XIIIa and produces an amino-terminal 56-kDa fragment and a 24-kDa fragment. The amino acid sequence of factor XIIIa is unique and does not exhibit internal homology, but its active center is similar to that of the thiol proteases. The probable Ca2+-binding site of factor XIIIa has been identified by homology to the high-affinity sites in calmodulins. Knowledge of the primary structure of factor XIIIa will aid elucidation of the mechanism of its enzymatic action and that of the many tissue transglutaminases of which it is the prototype. This will also facilitate production of factor XIIIa by recombinant DNA technology for use in treatment of congenital factor XIII deficiencies and in the postoperative healing of wounds.

‣ Long-Term faithful recapitulation of transglutaminase 1-deficient lamellar ichthyosis in a skin-humanized mouse model, and insights from proteomic studies

Aufenvenne, Karin; Rice, Robert H.; Hausse, Ingrid; Oji, V.; Hennies, Hans Crhristian; Río, Marcela del; Traupe, Heiko; Larcher Laguzzi, Fernando
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article
Publicado em 22/03/2012 Português
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This work was supported by the Bundesministerium für Bildung und Forschung as part of the Network for Rare Diseases NIRK (grant numbers: 01GM0901 and 01GM0902); the Foundation for Ichthyosis and Related Skin Types (F.I.R.S.T.); the National Institutes of Health (NIH) (grant number: P42 ES004699); and the Selbsthilfe Ichthyose e.V. FL was supported in part by the Instituto the Salud Carlos III (ISCIII) (grant number: PI081054), MDR was supported by the Ministerio de Ciencia y Innovación (MICINN) (grant number: SAF2010-16976). HCH was further supported by the Deutsche Forschungsgemeinschaft (DFG) (grant number: HE3119/5-1) and Köln Fortune (grant number: 79/2011)

‣ Protein-protein interactions in blood clotting. The use of polarization of fluorescence to measure the dissociation of plasma factor XIIIa.

Freyssinet, J M; Lewis, B A; Holbrook, J J; Shore, J D
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/02/1978 Português
Relevância na Pesquisa
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1. Human plasma Factor XIII (the precursor of fibrin-glutamine-fibrin-lysine endo-gamma-glutamyltransferase) was randomly labelled by incubation with fluorescein isothiocyanate. The biochemical properties of the system were unaltered by the label. The polarization of the fluorescein fluorescence attached to the plasma protein was measured and the following conclusions were reached. 2. Factor XIII (a'2b2) does not dissociate in the protein-concentration range 10-500 microgram/ml either with or without added Ca2+. 3. Factor XIIIa (a'2b2) does not dissociate in the absence of Ca2+ in the protein-concentration range 10-500 microgram/ml. 4. Additions of Ca2+ to Factor XIIIa result in a decreased polarization of fluorescence as the tetramer dissociates. The decrease in polarization was the same amplitude at protein concentrations 10-500 microgram/ml and Ca2+ concentrations 2-66 mM and indicates that the overall process is essentially irreversible. The decrease in polarization consisted of fast and slow exponential phases. Both the rate of the fast phase and the proportion of the reaction it represented increased with Ca2+ concentration. 5. A comparison of the rate of dissociation measured by fluorescence polarization and the rate of appearance of enzyme activity in the presence of a protein substrate suggests that the Factor XIII is autoactivated by a soluble a-subunit-containing molecular forming a tight complex with the substrate.

‣ Transport of glutamine by rat kidney brush-border membrane vesicles.

McFarlane-Anderson, N; Alleyne, G A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/08/1979 Português
Relevância na Pesquisa
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Transport of glutamine by brush-border vesicles prepared from the renal cortex was studied. The transport system had both Na+-dependent and Na+-independent components.The presence of Na+ in the incubation resulted in an 'overshoot' at 30s at which time the rates of transport were approx. 8 times the values obtained in the absence of Na+. Variation of the glutamine concentration showed that the system obeyed Michaelis-Menten kinetics with Km and Vmax. values for the Na+-dependent system of 0.86 mM and 9.6 nmol/min per mg of protein respectively. Vesicles obtained from chronically acidotic rats showed similar kinetic characteristics. The Km and Vmax. values for the Na+-dependent system were 0.76 mM and 9.6 nmol/min per mg of protein respectively. There was increased uptake of glutamine by vesicles from acidotic rats and this increase was associated with increased activity of gamma-glutamyltransferase in these preparations. Vesicles from acidotic rats, however, showed no increase in glucose transport and no increase in the activity of maltase, another brush-border enzyme.

‣ Cloning and nucleotide sequence of human gamma-glutamyl transpeptidase.

Rajpert-De Meyts, E; Heisterkamp, N; Groffen, J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1988 Português
Relevância na Pesquisa
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We have identified the gene for human gamma-glutamyl transpeptidase [GGT; glutamine:D-glutamyl-peptide 5-glutamyltransferase (also called gamma-glutamyltransferase), EC 2.3.2.2] in a BCR gene-related region located in band q11----qter of chromosome 22. Two cDNAs complementary to the GGT mRNA have been isolated from a human placental library constructed in phage lambda gt11. The largest cDNA has a size of 2535 base pairs (bp) and an open reading frame of 1707 nucleotides encoding 569 amino acids. By using a probe corresponding to this cDNA, a mRNA of approximately 2.4 kilobases was detected by RNA blot-hybridization analysis in mouse kidney RNA. The GGT precursor encoded by the coding sequence would have an estimated Mr of 61,400. We compared our nucleotide and deduced amino acid sequences with the published results of rat kidney cDNAs. The human and rat amino acid sequences are similar; however, a considerable discrepancy in nucleotide sequence was found within a 180-bp fragment of the heavy chain, resulting in a completely different amino acid sequence for this region. In addition, the 5' untranslated sequence of the human cDNA (669 bp) is substantially larger than that determined in the rat cDNA (227 bp). Our results may be valuable for further studies on the protein structure of human GGT as well as studies on the regulation of the enzyme.

‣ Three-dimensional structure of a transglutaminase: human blood coagulation factor XIII.

Yee, V C; Pedersen, L C; Le Trong, I; Bishop, P D; Stenkamp, R E; Teller, D C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 19/07/1994 Português
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Mechanical stability in many biological materials is provided by the crosslinking of large structural proteins with gamma-glutamyl-epsilon-lysyl amide bonds. The three-dimensional structure of human recombinant factor XIII (EC 2.3.2.13 zymogen; protein-glutamine:amine gamma-glutamyltransferase a chain), a transglutaminase zymogen, has been solved at 2.8-A resolution by x-ray crystallography. This structure shows that each chain of the homodimeric protein is folded into four sequential domains. A catalytic triad reminiscent of that observed in cysteine proteases has been identified in the core domain. The amino-terminal activation peptide of each subunit crosses the dimer interface and partially occludes the opening of the catalytic cavity in the second subunit, preventing substrate binding to the zymogen. A proposal for the mechanism of activation by thrombin and calcium is made that details the structural events leading to active factor XIIIa'.

‣ Cross-linked A alpha.gamma chain hybrids serve as unique markers for fibrinogen polymerized by tissue transglutaminase.

Murthy, S N; Lorand, L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1990 Português
Relevância na Pesquisa
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Notwithstanding the high degree of amino acid sequence homologies between human factor XIIIa on the one hand and intracellular transglutaminases (protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13) from guinea pig liver or human erythrocytes on the other, we find that the two sets of enzymes differ remarkably in the mode of cross-linking the same protein substrate--i.e., human fibrinogen. In the program of polymerization with factor XIIIa, production of the known gamma-gamma' homologous chain pairs is the dominant feature, whereas with either intracellular transglutaminase, a series of hitherto unidentified A alpha.gamma hybrid chain combinations, designated A alpha p gamma q (p and q = 1, 2, 3...), is generated and practically no gamma-gamma' dimers are formed. Two-dimensional electrophoresis is particularly useful for demonstrating the production of A alpha p gamma q structures by protein staining as well as by immunoblotting against specific antibodies to the A alpha and gamma chains of fibrinogen. These findings should aid in deciding whether the direct cross-linking of fibrinogen by transglutaminase might contribute to thrombotic processes in addition to the thrombin- and factor XIIIa-dependent pathway of clot formation.

‣ Identification of a new mutation (Gly420Ser), distal to the active site, that leads to factor XIII deficiency

Kangsadalampai, Sasichai; Yenchitsomanus, Pathai; Chelvanayagam, Gareth; Sawasdee, Nunghathai; Laosombat, Vichai; Board, Philip
Fonte: Munksgaard International Publishers Publicador: Munksgaard International Publishers
Tipo: Artigo de Revista Científica
Português
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The molecular defects of the factor XIII A subunit gene were studied in a patient with factor XIII deficiency. Mutation analysis was performed on amplified DNA from each exon of this gene by single-strand conformation polymorphism (SSCP) and DNA sequencing techniques. A substitution of guanine by adenine at nucleotide 1258 in exon 10 of the coagulation factor XIII A subunit gene has been identified in the patient. The mutation results in the replacement of Gly420 by Ser in the core domain of the enzyme. Restriction enzyme analysis of amplified exon 10 DNA confirmed that the patient was homozygous for this mutation. A family study revealed that the mutation was inherited from both parents, who were first cousins. The potential effects of the mutation were predicted by molecular modeling of the amino acid substitution within the coordinates of the crystal structure. The substitution occurred within the core domain of the enzyme at a residue completely conserved among all known members of the transglutaminase family. The model of the mutant protein suggests that although the substitution of Gly420 by Ser causes only minor readjustment of the residues and does not appear to be particularly deleterious in terms of structure, the mutation is...

‣ Identification and characterization of two missense mutations causing factor XIIIA deficiency

Kangsadalampai, S; Chelvanayagam, Gareth; Baker, Rohan; Kuperan, Ponnudarai; Board, Philip
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
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In this study, two amino acid substitutions. Arg260His and Val414Phe, have been identified in the factor XIIIA subunits of factor XIII deficient patients of Syrian and Indian descent, respectively. To confirm the deleterious effects of these substitutions, both variant sequences have been engineered into cDNA clones and the mutant enzymes expressed in yeast. Determination of the transglutaminase activity and immuno detection of the mutant enzymes together with mRNA hybridization revealed that the mutations dramatically reduce both the catalytic activity and the level of enzyme expressed in yeast. The mutations Arg260His and Val414Phe occur within the 'core' domain of the enzyme. Computer modelling of the mutant enzymes reveals that the substitution of the Arg260 by His results in the loss of a conserved electrostatic interaction whereas the effect of the Val414Phe substitution is a consequence of the large increase in side-chain volume. Although both mutations do not effect the active site directly, they are predicted to reduce the stability of the enzyme. The effects of these two amino acid substitutions on enzyme expression and three-dimensional structure strongly confirm that residues which are located outside of the active site can have a significant effect on protein stability and function.