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PubMed1976

Conformation and reactivity of DNA in the complex with protein. IV. Circular dichroism of poly-L-histidine model complexes with DNA polymers and specificity of the interaction.

The CD study of the DNA-poly-L-histidine complex at high degree of protonation revealed that complex formation is already observable at 2 M NaCl. The influence of salt together with 5 M urea suggests that in addition to electrostatic interactions probably hydrogen bonding may favour specific complexes. Affinity of protonated histidines to AT-rich regions is strongly supported by the complexes formed with (dA.dT)-containing polymers. The psi-type structure occurs with poly(dA-dT)-poly(dA-dT) while poly(dA)-poly(dT) is restricted to form a similar psi-state on interaction with highly protonated poly-L-histidine. Differences in the helix winding properties due to variation in the sequence is suggested as a possible factor in the formation of the psi-type complexes. The mechanism of interaction including hydrogen bonding of histidine side-chains with an AT pair at high degree of protonation and with GC-regions at lower degree of protonation in the polypeptide structure is discussed.

Binding Sites↗
PubMed1977

Purification and characterization of a complex between cloacin and its immunity protein isolated from Enterobacter cloacae (Clo DF13). Dissociation and reconstitution of the complex.

Cell of Enterobacter cloacae (Clo DF13) produce a bacteriocin which is characterized by its very effective killing activity against sensitive bacteria. Purification and characterization of the excreted bacteriocin has revealed that this bacteriocin consists of an equimolar complex of two plasmid-specific gene products: the cloacin and its inhibitor the immunity protein. Dissociation of the complex by treatment with sodium dodecylsulfate induces the endonucleolytic activity of the cloacin but strongly reduces the killing activity. The purified complex possesses no activity in vitro. Both cloacin and immunity protein isolated from the complex were functionally identical to cloacin and immunity protein purified from the bacteriocinogenic cells by other methods. Reconstitution of the complex results in a partial restoration of killing activity.

Amino Acids↗
PubMed2004

Ternary complex factor-serum response factor complex-regulated gene activity is required for cellular proliferation and inhibition of apoptotic cell death.

Members of the ternary complex factor (TCF) subfamily of the ETS-domain transcription factors are activated through phosphorylation by mitogen-activated protein kinases (MAPKs) in response to a variety of mitogenic and stress stimuli. The TCFs bind and activate serum response elements (SREs) in the promoters of target genes in a ternary complex with a second transcription factor, serum response factor (SRF). The association of TCFs with SREs within immediate-early gene promoters is suggestive of a role for the ternary TCF-SRF complex in promoting cell cycle entry and proliferation in response to mitogenic signaling. Here we have investigated the downstream gene regulatory and phenotypic effects of inhibiting the activity of genes regulated by TCFs by expressing a dominantly acting repressive form of the TCF, Elk-1. Inhibition of ternary complex activity leads to the downregulation of several immediate-early genes. Furthermore, blocking TCF-mediated gene expression leads to growth arrest and triggers apoptosis. By using mutant Elk-1 alleles, we demonstrated that these effects are via an SRF-dependent mechanism. The antiapoptotic gene Mcl-1 is identified as a key target for the TCF-SRF complex in this system. Thus, our data confirm a role for TCF-SRF-regulated gene activity in regulating proliferation and provide further evidence to indicate a role in protecting cells from apoptotic cell death.

Alleles↗
PubMed1992

The serpin-enzyme complex (SEC) receptor mediates the neutrophil chemotactic effect of alpha-1 antitrypsin-elastase complexes and amyloid-beta peptide.

The serpin-enzyme complex (SEC) receptor mediates catabolism of alpha 1-antitrypsin (alpha 1-AT)-elastase complexes and increases in synthesis of alpha 1-AT in cell culture. The SEC receptor recognizes a pentapeptide domain on alpha 1-AT-elastase complexes (alpha 1-AT 370-374), and the same domain in several other serpins, amyloid-beta peptide, substance P, and other tachykinins. Thus, it has also been implicated in the biological properties of these ligands, including the neurotoxic effect of amyloid-beta peptide. In this study, we examined the possibility that the SEC receptor mediates the previously described neutrophil chemotactic activity of alpha 1-AT-elastase complexes, and whether the other ligands for the SEC receptor have neutrophil chemotactic activity. The results show that 125I-peptide 105Y (based on alpha 1-AT 359-374) binds specifically and saturably to human neutrophils, and the characteristics of this binding are almost identical to that of monocytes and hepatoma-derived hepatocytes. Peptide 105Y and amyloid-beta peptide mediate chemotaxis for neutrophils with maximal stimulation at 1-10 nM. Mutant or deleted forms of peptide 105Y, which do not bind to the SEC receptor, have no effect. The neutrophil chemotactic effect of alpha 1-AT-elastase complexes is blocked by antiserum to peptide 105Y and by antiserum to the SEC receptor, but not by control antiserum. Preincubation of neutrophils with peptide 105Y or substance P completely blocks the chemotactic activity of amyloid-beta peptide, but not that of FMLP. These results, therefore, indicate that the SEC receptor can be modulated by homologous desensitization and raise the possibility that pharmacological manipulation of this receptor will modify the local tissue response to inflammation/injury and the neuropathologic reaction of Alzheimer's disease.

Alzheimer Disease↗
PubMed1979

Studies on the nuclear binding of steroid hormone-receptor complex; characteristics of binding of nuclei from fetal rat liver to 3H-dexamethasone-liver cytoplasmic receptor complex.

Binding of 3H-dexamethasone (Dex)-rat liver cytoplasmic receptor complex to nuclei from fetal rat livers in vitro exhibited a high-affinity and saturable nature (Kd=1.5 X 10- M, maximal binding sites=470 fmole/mg DNA), and the binding was inhibited competitively by prior injection of Dex in vivo. While binding of 3H-Dex-receptor complex to nuclei from adult rat liver was in low affinity and unsaturable, and injection of Dex prior to the sacrifice of animals did not influence the nuclear binding to 3H-Dex-receptor complex in vitro. Differential salt-extraction with KCl solution of the nuclear bound 3H-Dex receptor complex revealed the presence of salt-extractable and residual forms of bound receptors. The amount of the fraction extracted with 0.3 M KCl reached its maximum at 10 min after the start of incubation, while the 1.0 M KCl-extractable and residual fractions reached their maximum plateaus after 30 min of the incubation. Scatchard analysis revealed that the binding of the receptor complex to the 0.3M and 1.0M KCl fractions was saturable, while the residual fraction did not show any tendency of saturation under the experimental conditions employed in the present study. The results obtained in this work were compared to those which have been reported by other investigators.

Animals↗
PubMed1992

Heparin-binding properties of vitronectin are linked to complex formation as illustrated by in vitro polymerization and binding to the terminal complement complex.

Vitronectin (VN, complement S-protein) is a multifunctional protein which participates in cell adhesion, coagulation, fibrinolysis, and protection against complement lysis. VN is incorporated into several complexes, such as the terminal complement complex and thrombin-antithrombin III, and is bound to plasminogen activator inhibitor 1. The present study showed that purified VN spontaneously forms polymers of approximately 1000 kDa with a Stokes radius of 10 nm. The polymers are to a varying extent stabilized by disulfide bonds, but are quite stable even after reduction and alkylation, indicating the importance of noncovalent bonds. Plasma VN circulates mainly as a 65/75-kDa monomer containing a cryptic heparin-binding site which is exposed upon a conformational change induced by different stimuli, such as coagulation, heating, adsorption to surfaces, or exposure to acids, urea, or other denaturating agents. In the present study, VN was demonstrated to expose its heparin-binding site and its conformationally dependent 8E6 epitope when incorporated into the terminal complement complex. We suggest that exposure of the heparin-binding site and a putative hydrophobic binding site of VN are linked events dependent upon the same conformational change. In vivo, complex formation probably induces the heparin-binding site. Such a link might also explain why purified heparin-binding VN spontaneously forms polymers. The heparin-binding site may be involved in the elimination of multimolecular complexes containing VN.

Antibodies, Monoclonal↗
PubMed1992

Protease composition of exocytosed human skin mast cell protease-proteoglycan complexes. Tryptase resides in a complex distinct from chymase and carboxypeptidase.

We characterized the release and the protease composition of high m.w. complexes released from dispersed human skin mast cells, under conditions that did not disrupt the binding of proteases to proteoglycan. The net percent release ratio of tryptase to histamine, after anti-IgE and calcium ionophore A23187 stimulation was higher than those for chymase or carboxypeptidase. This was explained by the greater cell association of carboxypeptidase and chymase, compared with tryptase, after mast cell degranulation and/or differential cosedimentation of the proteases with mast cells, because treatment of activated mast cells with 1 M NaCl increased the release ratios of chymase and carboxypeptidase more than that of tryptase. Tryptase, after release, was stable in 0.12 M NaCl and had a molecular mass of approximately 200 to 250 kDa, suggesting that it was bound to proteoglycan. We demonstrated that complexes containing chymase and carboxypeptidase were separable from tryptase-containing complexes by gel filtration and by affinity chromatography. First, on fast protein liquid chromatography, released tryptase filtered at a molecular mass of approximately 200 to 250 kDa, compared with chymase and carboxypeptidase at 400 to 560 kDa. Second, by using affinity chromatography with immobilized antitryptase mAb in 0.15 M NaCl, carboxypeptidase and chymase activities were recovered primarily in the effluent and washes of an antitryptase antibody affinity column and cofiltered at 400 to 560 kDa. Tryptase was recovered only in the eluate. Finally, by using potato tuber carboxypeptidase inhibitor-Sepharose affinity chromatography, tryptase activity was found primarily in the effluent and washes, filtered at a molecular mass of 200 kDa on fast protein liquid chromatography, and was stable in 0.12 M NaCl buffer at 37 degrees C. Carboxypeptidase and chymase activities were found primarily in the eluate. These findings suggest that tryptase and carboxypeptidase/chymase reside in distinct macromolecular complexes. Separate complexes containing these proteases may help explain previous ultrastructural observations in which the distributions of chymase and tryptase within a single granule did not always coincide.

Carboxypeptidases↗
PubMed1977

Immunologic properties of protein-lipopolysaccharide complexes. I. Antibody response of normal, thymectomized, and nude mice to a lysozyme-lipopolysaccharide complex.

The in vivo antibody response to the lysozyme component of a lysozyme-lipopolysaccharide complex has been investigated in normal, thymectomized and nude mice. The splenic PFC response elicited by the complex in CBA mice is 10- to 20-fold higher than the response elicited by lysozyme admixed with LPS. Both lysozyme-LPS complexes and lysozyme + LPS mixtures prime mice for a subsequent secondary anti-lysozyme response. In contrast, thymectomized mice responded poorly to lysozyme-LPS complexes unless reconstituted with splenic T cells. However, nude mice responded as well as Nu/+ controls to the complex. The PFC response of normal and of nude mice was severely depressed by treatment with anti-lymphocyte serum. These findings suggest that T lymphocytes contribute significantly to the enhanced immune responsiveness associated with LPS administration.

Animals↗
PubMed1979

Passive immune complex glomerulonephritis in mice: models for various lesions found in human disease. I. High avidity complexes and mesangiopathic glomerulonephritis.

Intravenous injection of mice with soluble complexes of highly avid rabbit antibody to egg albumin, prepared by dissolution of equivalence precipitates in large quantities of antigen, resulted in a purely mesangial localization of the complexes. When animals received three injections of complexes per day for 1 day it was noted that precipitates dissolved in 80 times the equivalence amount of antigen produced slight mesangial changes. When such complexes were injected for 2 or 3 days, outright mesangiopathic glomerulonephritis was observed in an increasing proportion of the animals. Equivalent amounts of antigen alone did not produce lesions.

Animals↗
PubMed1991

Decreased activities of ubiquinol:ferricytochrome c oxidoreductase (complex III) and ferrocytochrome c:oxygen oxidoreductase (complex IV) in liver mitochondria from rats with hydroxycobalamin[c-lactam]-induced methylmalonic aciduria.

Rats treated with hydroxycobalamin[c-lactam] (HCCL), a cobalamin analogue that induces methylmalonic aciduria, have increased hepatic mitochondrial content and increased oxidative metabolism of pyruvate and palmitate per hepatocyte. The present studies were undertaken to characterize oxidative metabolism in isolated liver mitochondria from rats treated with HCCL. After 5-6 weeks, state 3 oxidation rates for diverse substrates are reduced in mitochondria from HCCL-treated rats. Similar reductions of mitochondrial oxidation rates are obtained with dinitrophenol-uncoupled mitochondria excluding defective phosphorylation as a cause for the observed decrease in mitochondrial oxidation. The activities of mitochondrial oxidases are reduced in HCCL-treated rats and demonstrate a defect in complex IV. Investigation of the complexes of the respiratory chain reveals a 32% decrease of ubiquinol:ferricytochrome c oxidoreductase (complex III) activity and a 72% decrease of ferrocytochrome c:oxygen oxidoreductase (complex IV) activity in mitochondria from 5-6-week HCCL-treated rats as compared with controls. Liver mitochondria from HCCL-treated rats also demonstrate decreased cytochrome content per mg of mitochondrial protein (25% decrease of cytochrome b and 52% decrease of cytochrome a + a3 as compared with control rats). The HCCL-treated rat represents an animal model for the study of the consequences of respiratory chain defects in liver mitochondria.

Animals↗
PubMed1975

Endogenous immune complex nephropathy associated with malignancy I. Studies on the nature and immunopathogenic significance of glomerular bound antigen and antibody, isolation and characterization of tumor specific antigen and antibody and circulating immune complexes.

Three patients with clear cell renal carcinoma and one with another intrarenal malignancy were studied for the presence of glomerular localized immunoglobulins, complement components and tumor specific antigen and antibody by immunofluorescence. To determine the association and elucidate the pathogenic mechanisms involved in the relationship between tumors and glomerular deposits, antibody eluted from tumor tissue and renal glomeruli, cryoproteins, serum antibodies and rabbit antisera to tumor tissue were tested for specificity to antigen. The relationship between tumor antigens and the lipoprotein antigen localized in normal proximal tubular brush border (RTE) and the small bowel mucosa, was studied by immunofluorescence, absorption and blocking studies as well as complement fixation. Immunoglobulins and complement components were localized in the glomeruli and tumor membrane of all patients. Sera and glomerular fixed antibody from three patients with renal cell carcinoma localized to normal proximal tubular brush border and jejunal mucosa as well as to tumor membrane and the glomeruli and proximal tubules of all of these three patients. Anti RTE activity was also detected by complement fixation. Immunologic similarity between RTE and renal cell carcinoma antigen was confirmed by absorption studies. Furthermore, cryoprecipitable complexes of tumor antigen and specific antibody were isolated from the serum. The tumor antibody was immunologically similar to RTE. In the other case the rabbit anti-tumor antibody and the patient's serum fixed to the tumor membrane and kidney of the patient but did not show cross reactivity with the renal cell carcinoma or RTE. These studies suggest that the tumor antigen in renal cell carcinoma is similar to RTE and the glomerular deposits represent tumor antigen and antibody complexes. In addition these investigations support the hypothesis that tumor immune complexes are significant in the glomerular lesions, and that the origin of renal cell carcinoma is in the proximal tubule. The investigations also show that tumor antibodies are specific for tumors of the same morphological type but not for other tumors in the same tissue. Moreover, the renal glomerulus appears to be a chosen anatomic site for deposition of tumor antigens and antibodies and studies of the kidney may provide insight into the nature of tumor antigens and antibodies. Cryoprecipitation appears to be a valuable method in isolation of tumor complexes and characterization of tumor specific antigen and antibody.

Absorption↗
PubMed1977

Experimental studies on factors causing acute serum sickness glomerulonephritis of immune complex origin. I. The role of immune complexes and the immunological status of the host.

In acute serum sickness glomerulonephritis induced in rabbits by large doses of BSA, the relationship of the host's immunological status and the severity of renal histological changes was studied. It was found that good antibody producers developed more severe renal lesions. The higher avidity of antibodies enhances the inflammatory effect of immune complexes. Kidney is favoured for deposition of immune complexes especially in the case of chronic immune complex formation in the presence of antigen excess. Diminished phagocytic function of leukocytes (probably decreased immune complex saturating capacity) may also contribute to the severity of renal histological alterations.

Acute Disease↗
PubMed1978

The use of the preparation of F(ab')2 antibody from soluble immune complexes to determine the complexed antigens.

An autoradiographic technique for the characterization of antibody specificity in soluble antigen--antibody complexes has been developed. The circulating antigen--antibody complexes are precipitated by polyethylene glycol (PEG). The antibodies are liberated as F(ab')2 from the complexes by pepsin digestion. The antibody specificity against the putative antigen was revealed by radioimmunoelectrophoresis using [125I]-F(ab')2 reagents. The method was developed by using an experimental model of C3/anti-C3 complexes.

Animals↗
PubMed1978

Fc receptor bearing 'hairy cells' of leukaemic reticuloendotheliosis bind soluble antigen--antibody complexes and adhere to immobilized complexes, but fail to mediate antibody dependent cellular cytotoxicity.

The majority of hairy cells from three patients with leukaemic reticuloendotheliosis were adherent cells bearing surface immunoglobulin, complement receptors, and Fc receptors. Highly purified populations of malignant hairy cells, which readily bound soluble antigen-antibody complexes in suspension and were able to adhere to immobilized antigen-antibody complexes, were examined for their ability to mediate ADCC. Two patients with greater than 90% FcR positive cells failed to mediate ADCC. When initially examined, a third patient, with fewer malignant cells, demonstrated a less marked impairment of cytolysis. When reexamined at a later date, this patient had an increased number of hairy cells and concomitantly demonstrated more impaired ADCC effector cell activity. Absorption of surface immunoglobulin bearing cells onto plastic surfaces coated with goat anti-human immunoglobulin resulted in a complete depletion of FcR, sIg positive, hairy cells. The remaining nonadherent fraction, containing 5.5% FcR positive, sIg negative cells, was able to mediate ADCC as effectively as the normal controls. These results indicate that although FcR bearing hairy cells readily bind soluble antigen-antibody complexes and adhere to immobilized complexes, they were unable to mediate ADCC.

Adult↗
PubMed1979

Antibody--antigen complex stimulated lysis of non-sensitized sheep red cells by human lymphocytes. I. Requirements for IgG complexes.

IgG antibody--antigen complexes stimulated lysis of non-sensitized sheep erythrocytes (SRBC) by normal human peripheral blood lymphocytes (PBL). Heat-aggregated human IgG, rabbit IgG-ovalbumin complexes and rabbit IgG-sensitized ox erythrocytes (ORBC) were effective in the induction of SRBC lysis by PBL. However, IgM-sensitized ORBC and IgM-complement-sensitized ORBC were ineffective. As only SRBC and not ORBC or chicken erythrocytes (CRBC) were lysed under identical experimental conditions, it is conceivable that the SRBC receptor present on the T cell is involved. Furthermore, 45% inhibition of lysis was obtained by pretreating the effector cells with anti-human thymocyte globulin (ATG) and complete inhibition was obtained by adding SRBC stroma to the reaction mixture. The requirement for the inclusion of IgG complexes and the absence of specific anti-target cell antibody distinguish this reaction from natural cell-mediated cytotoxicity and antibody-dependent cell-mediated cytotoxicity (ADCC). Immune killer T cells would not appear to be responsible as eight different donors were used and none of these were cytotoxic to SRBC in the absence of IgG complexes. The induction of this cytotoxic reaction appears to require the recognition and interaction by the effector cells of two separate molecular entities, i.e. the SRBC membrane by the T cell and the IgG Fc region by an IgG-Fc receptor-bearing cell.

Animals↗
PubMed1975

The structure of the complex formed by bovine trypsin and bovine pancreatic trypsin inhibitor III. Structure of the anhydro-trypsin-inhibitor complex.

The structure of the complex between anhydro-trypsin and pancreatic trypsin inhibitor has been determined by difference Fourier techniques using phases obtained from the native complex (Huber et al., 1974). It was refined independently by constrained crystallographic refinement at 1.9 A resolution. The anhydro-complex has Ser 195 converted to dehydro-alanine. There were no other significant structural changes. In particular, the high degree of pyramidalization of the C atom of Lys 15 (I) of the inhibitor component observed in the native complex in maintained in the anhydro-species.

Amino Acids↗
PubMed1992

A possible in vivo mechanism of intermediate transfer by glycolytic enzyme complexes: steady state fluorescence anisotropy analysis of an enzyme complex formation.

Rate constants of dissociation (k(off)) and association (k(on)) of the bienzyme complex yeast glyceraldehyde-3-phosphate dehydrogenase--yeast alcohol dehydrogenase have been determined in the absence and presence of NAD or NADH by fluorescence anisotropy measurements. We found that dissociation of the complex is considerably slower than catalytic turnover of either of the enzymes (that is k(off) much less than kcat) irrespective of the presence of coenzymes. A perusal of the literature reveals that this relation invariably applies to all systems studied so far. These observations all taken together constitute compelling evidence that direct metabolite transfer in enzyme complexes cannot be satisfactorily described by invoking the dynamic model but requires a model assuming more lasting complexes. This seems to support the case of the temporary-stationary model suggested by one of us. Implications of this conclusion are treated in depth and further evidence is cited under Discussion.

Alcohol Dehydrogenase↗
PubMed1992

Stable superoxide dismutase (SOD)-mimetic ternary human serum albumin-Cu(II)(3,5-diisopropylsalicylate)2/Cu(II)2(3,5-diisopropylsalicylate)4 complexes in tissue distribution of the binary complex.

Copper(II)2(3,5-diisopropylsalicylate)4 [Cu(II)2(3,5-DIPS)4] has been found to have antiinflammatory, antiulcer, anticancer, anticonvulsant, antimutagenic, antidiabetic, analgesic, and radiation protection and recovery activities. It has also been found to reduce ischemia-reperfusion injury. Because of these activities it was of interest to understand how this compound is transported in the body to affected tissues. Evidence supporting the suggested formation of ternary human serum albumin (HSA)-Cu(II)(3,5-DIPS)2 or Cu(II)2(3,5-DIPS)4 complexes was obtained using ultraviolet spectrophotometry, dialysis, and atomic absorption spectrophotometry or atomic emission spectroscopy. Superoxide dismutase (SOD)-mimetic activity was also determined using the xanthine/xanthine oxidase/cytochrome c system. Ultraviolet spectra of aqueous solution mixtures of Cu(II)2(3,5-DIPS)4 in equilibrium with 2Cu(II)(3,5-DIPS)2 and HSA as well as aqueous solutions of solid Cu(II)2(3,5-DIPS)4 obtained by stirring the solid with an aqueous solution of HSA showed no obvious change in absorbance to indicate ternary complex formation. However, comparison of ultraviolet spectra taken before and after dialysis supports the suggested bonding of Cu(II)(3,5-DIPS)2 or Cu(II)2(3,5-DIPS)4 to HSA. Comparison of copper concentrations before and after dialysis also supports the suggested bonding of Cu(II)(3,5-DIPS)2 or Cu(II)2(3,5-DIPS)4 to HSA. Based upon these data it is plausible that Cu(II)(3,5-DIPS)2 or Cu(II)2(3,5-DIPS)4 form stable ternary complexes with HSA. These stable ternary complexes were also found to have SOD-mimetic activity.

Copper↗