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PubMed2004

Characterization of a complex formed between human plasminogen and recombinant sheep prion: pressure and thermal sensitivity of complex formation.

Scrapie is thought to be caused by one or more conformations of a proteinacious particle called a prion. The infectious form(s) is referred to as the scrapie form of the prion protein (PrPsc) whereas a benign form, the cellular conformer, is referred to as PrPC. The cellular conformation of the sheep prion protein formed a 1:1 complex with human plasminogen. The complex precipitated at 0 degrees C (Ksp = 17* 10(-12) M2). This precipitation reaction was sensitive to both temperature and pressure. When subjected to hydrostatic pressure the precipitate dissolved. At 25 degrees C the complex was soluble with a dissociation constant of about 10(-7) M as determined by isothermal titration calorimetry. Absorption, fluorescence and circular dichroism spectroscopy showed that neither protein, in the complex, underwent a detectable structural change so long as proteolytic inhibitors were present. In the absence of proteolytic inhibitors, plasminogen slowly cleaved the prion protein.

Animals↗
PubMed2004

[Synthesis of mixed complexes of lanthanum with 2,2-bipyridyl and 1,10-phenanthroline and study of the interaction of the complexes with DNA].

A mixed complex of La with 2,2-bipyridyl (dpy) and 1,10-phenanthroline(phen) was synthesized. Elemental analysis, IR and TGA of the complex were investigated, thus it was proved that the conformation of it was La(dpy)(phen)Cl3. The interaction of the complex with DNA has been studied also. The spectra showed that the interaction between La(dpy)(phen)Cl3 and DNA experienced intercalation of long-range self-assembly. The study made it clear that the synthesized mixed complex La(dpy)(phen)Cl3 can interact with DNA, and La(dpy)(phen)Cl3 can be used for probing a nucleic acid.

2,2'-Dipyridyl↗
PubMed1999

[Study on luminescence of the serial new ternary or tetradic complexes complexes of Eu (III) with beta-diketone].

The UV absorption, fluorescence, unstable spectra and quantum yields of five ternary or tetradic complexes of Eu (III) with beta-diketone (dibenzoyl methane, thenoyltrifluoroacetone), acrylic acid and other ligands were reported. The influences of the first and second ligands on absorption and luminescence spectra were found. The lifetimes and the processes of energy transfer of Eu3+ from 5D1 to 5D0 in complex solutions were measured. It was found that the lifetimes of Eu3+ complexes with TTA are approximate to each other and larger than those of complexes with DBM.

English Abstract↗
PubMed1990

[Apatite-collagen complex. Preparation of a new apatite-collagen complex].

A new apatite-collagen complex was prepared in calcium beta-glycerophosphate solutions at pH 8.50. For this preparation, reconstituted type I collagen was cross-linked with phosvitin in the presence of alkaline phosphatase by use of a cross-linking agent of dimethyl suberimidate. After two weeks of immersion in daily-renewed solution of calcium beta-glycerophosphate, the complex contained apatite approximately two times the modified collagen in weight. When viewed in a scanning electron microscope, needle-like crystals precipitated densely on the collagen fibrils. However, in some portion of the complex, dot-like precipitate was observed as well. X-ray diffraction and IR analyses of the complex suggested that the apatite precipitated on the collagen fibrils was very similar to bone mineral in two aspects, crystallinity and carbonate content.

Apatites↗
PubMed1986

Cultured human endothelial cells synthesize a plasma membrane protein complex immunologically related to the platelet glycoprotein IIb/IIIa complex.

We have previously demonstrated that endothelial cells synthesize a plasma membrane protein indistinguishable from platelet glycoprotein (GP) IIa. The present study provides evidence for a further analogy between the platelet and the endothelial cell membrane by showing that cultured endothelial cells also synthesize a membrane protein complex immunologically related to the platelet GP IIb/GP IIIa complex. This evidence is based on the following observations: (1) C17, a murine monoclonal antiplatelet GP IIIa antibody, consistently precipitates two proteins, apparent molecular weights, respectively, 115,000 and 125,000 reduced and 95,000 and 135,000 nonreduced, from metabolically (35S-methionine) as well as surface 125I-labeled cultured human endothelial cells; (2) upon crossed immunoelectrophoresis of solubilized endothelial cells against a polyclonal rabbit antiplatelet antiserum and 125I-labeled C17 IgG, a single precipitate of the protein(s) recognized by C17 is observed. As judged by their mobility in 9% polyacrylamide gels, both endothelial proteins appear to have a somewhat larger molecular weight than their platelet counterparts. Patterns obtained by crossed immunoelectrophoresis are also indicative of a difference in electrophoretic behavior of the platelet GP IIb/IIIa complex and the endothelial cell protein complex.

Blood Platelets↗
PubMed1988

Affinity labeling the DNA polymerase alpha complex. I. Pyridoxal 5'-phosphate inhibition of DNA polymerase and DNA primase activities of the DNA polymerase alpha complex from Drosophila melanogaster embryos.

DNA polymerase alpha from Drosophila melanogaster embryos is a multisubunit enzyme complex which can exhibit DNA polymerase, 3'----5' exonuclease, and DNA primase activities. Pyridoxal 5'-phosphate (PLP) inhibition of DNA polymerase activity in this complex is time dependent and exhibits saturation kinetics. Inhibition can be reversed by incubation with an excess of a primary amine unless the PLP-enzyme conjugate is first reduced with NaBH4. These results indicate that PLP inhibition occurs via imine formation at a specific site(s) on the enzyme. Results from substrate protection experiments are most consistent with inhibition of DNA polymerase activity by PLP binding to either one of two sites. One site (PLP site 1) can be protected from PLP inhibition by any nucleoside triphosphate in the absence or presence of template-primer, suggesting that PLP site 1 defines a nucleotide-binding site which is important for DNA polymerase activity but which is distinct from the DNA polymerase active site. PLP also inhibits DNA primase activity of the DNA polymerase alpha complex, and primase activity can be protected from PLP inhibition by nucleotide alone, arguing that PLP site 1 lies within the DNA primase active site. The second inhibitory PLP-binding site (PLP site 2) is only protected from PLP inhibition when the enzyme is bound to both template-primer and correct dNTP in a stable ternary complex. Since binding of PLP at site 2 is mutually exclusive with template-directed dNTP binding at the DNA polymerase active site, PLP site 2 appears to define the dNTP binding domain of the active site. Results from initial velocity analysis of PLP inhibition argue that there is a rate-limiting step in the polymerization cycle during product release and/or translocation.

Affinity Labels↗
PubMed1985

The membrane attack complex of complement: C5b-8 complex as accelerator of C9 polymerization.

Polymerization of C9 occurs spontaneously or can be induced by the tetramolecular complex C5b-8. Spontaneous C9 (0.15 mg/ml) polymerization required more than 3 days at 37 degrees C. In the presence of C5b-8, C9 polymerization was complete within 10 min. The molar C9:C5b-8 ratio determined the extent of tubular poly C9 formation by C5b-8-bearing phospholipid vesicles. When this ratio was 9:1 or 12:1, 72% of complex-bound C9 was present as SDS resistant tubular poly C9 (Mr = 1.1 X 10(6]. At lower C9:C5b-8 ratios, poly C9 was bound primarily in nontubular form. Tubular poly C9, as part of C5b-9, could also be generated on rabbit erythrocytes by using whole human serum as a complement source. At limiting serum concentration (molar C9 to C8 ratio approximately 2), no SDS-resistant tubular poly C9 was detected. At high serum concentration or when using serum that was supplemented with C9, up to 40% of the C9 was SDS-resistant tubular poly C9, and the rest was poly C9, which was incompletely polymerized. It is suggested that the C5b-8 complex acts as an accelerator of C9 polymerization, and that its relative concentration to C9 determines the ultrastructure of the C5b-9 complex.

Animals↗
PubMed1979

Crystallization and preliminary crystallographic data of chicken gizzard G-actin . DNase I complex and Physarum G-actin . DNase I complex.

Smooth muscle G-actin from chicken gizzard and Physarum plasmodium G-actin both interact with DNase I and form 1 : 1 complexes. These complexes were crystallized by using polyethylene glycol 6000 as a precipitant. Both crystals belong to the same orthorhombic space group P2(1)2(1)2(1). The cell dimensions of chicken gizzard G-actin.DNase I complex are a=42.00 +/- 0.07 A, b=225.3 +/- 0.4 A, and c=77.4 +/- 0.1 A, while those of Physarum G-actin.DNase I complex are a=42 A, b=221 A, and c=77 A.

Actins↗
PubMed1981

Studies on the interaction of Trasylol (aprotinin) with trypsin-pancreatic secretory trypsin inhibitor (PSTI) complexes and with alpha 2-macroglobulin-trypsin-PSTI-complexes.

An investigation was performed to study the interaction of Trasylol with both trypsin-pancreatic secretory trypsin inhibitor (PSTI) and alpha 2-macroglobulin (alpha 2-M)-trypsin-PSTI complexes. Trasylol was readily able to displace immunogenic PSTI from a complex with trypsin in vitro. A similar scale of displacement of PSTI by Trasylol from alpha 2-M-trypsin-PSTI complexes could not be demonstrated. Using complexes manufactured in vitro with 125I-labelled PSTI, we found that only a small percentage of the PSTI label could be liberated, even when presented with amounts of Trasylol in a 10-molar excess to the PSTI.

Aprotinin↗
PubMed1983

Isolation of human complex-forming glycoprotein, heterogeneous in charge (protein HC), and its IgA complex from plasma. Physiochemical and immunochemical properties, normal plasma concentration.

Human complex-forming glycoprotein, heterogeneous in charge (protein HC) has previously been isolated from urine and immunochemically shown to be present in low and high molecular weight forms in blood plasma (Tejler, L., and Grubb, A. O. (1976) Biochim. Biophys. Acta 439, 82-94). In the present work, the major low and high molecular weight forms of the protein were isolated from plasma by immunosorption followed by gel chromatography. The plasma low molecular weight protein HC and the urinary protein had similar, if not identical, molecular weight, amino acid composition, NH2-terminal and carboxyl-terminal amino acid sequences and electrophoretic mobility. The low molecular weight plasma protein HC carried a yellow chromophore like the urinary protein, but its molar extinction coefficient at 280 nm was lower and its charge heterogeneity less pronounced than that of urinary protein HC. The plasma high molecular weight protein HC had a hydrodynamic volume which was greater than that of monomeric IgA but smaller than that of dimeric IgA. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the isolated high molecular weight protein followed by electrophoretic blotting and immunochemical analysis demonstrated that the protein contained four polypeptide chains: two light immunoglobulin chains (Mr = 23,000), one IgA alpha-chain (Mr = 54,000), and one chain with Mr approximately 90,000 which carried both alpha-chain and protein HC antigenic determinants. Whether the protein HC X IgA complex is a functionally significant part of the humoral immune system cannot be decided without further experimentation, but the complex was found to be completely absent from the blood plasma of patients with a selective deficiency of IgA-secreting immunocytes. The isolated low and high molecular weight plasma protein HC components were used as standard proteins in the construction of a quantitative crossed immunoelectrophoretic assay for the simultaneous quantitation of the two major protein HC components in blood plasma. The plasma concentrations of the low and high molecular weight protein HC components were measured by this method in 13 healthy Caucasians. The results for the low molecular weight protein HC were: mean, 20.3 mg/liter, S.D., 3.2 mg/liter, range, 13.6-26.0 mg/liter; and for the protein HC X IgA complex: mean, 293 mg/liter, S.D., 176 mg/liter, range, 36-620 mg/liter.

Adult↗
PubMed1984

Direct comparison of the rates of internalization and degradation of covalent receptor-insulin complexes in 3T3-L1 adipocytes. Internalization of occupied receptors is not the rate-limiting step in receptor-hormone complex degradation.

Insulin receptors on the surface of 3T3-L1 adipocytes were photolabeled using the iodinated analog, B29-lysine-substituted N-[N'-(2-nitro-4-azidophenyl)glycyl]insulin. Under optimal labeling conditions (below 15 degrees C), greater than 95% of the labeled receptor remained on the cell surface prior to incubation at 37 degrees C. When the labeled monolayers were returned to their normal culture environment (37 degrees C), the covalent receptor-insulin complexes were rapidly internalized at initial rates equivalent to 130-170% of labeled surface receptor/h. Internalization of the complexes proceeded to an equilibrium or end point distribution of 40% internal receptor and 60% cell-surface receptor. Under the several labeling conditions tested, covalent receptor-insulin complexes were degraded in an apparent first order process at 37 degrees C with half-lives between 5 and 7 h. This rate was equivalent to only 10% of the labeled receptor being degraded per h and was 13-17-fold slower than the initial rate of labeled receptor internalization. This study directly demonstrates that the initial rate of internalization of covalent receptor-insulin complexes is not the rate-limiting step in their degradation in 3T3-L1 adipocytes. Furthermore, 3T3-L1 adipocytes are unable to internalize all of the labeled surface receptor, suggesting that two classes of internalization competent and incompetent receptor may exist or that an equilibrium distribution of internal and cell-surface receptor is established by the relative rates of internalization and recycling of labeled receptor.

Adipose Tissue↗
PubMed1980

Circulating protein complexes in D-penicillamine therapy of rheumatoid arthritis. Correlation between IgG- and alpha 1-antitrypsin-IgA complexes and clinical response.

Eighteen of 24 patients with rheumatoid arthritis showed intermediate IgG-containing complexes on preparative ultracentrifugation before treatment with D-penicillamine. Serial analyses of these showed strikingly close correlation in reduction of IgG as well as alpha 1-antitrypsin-IgA complexes. Three patients did not respond to treatment clinically, and retained both types of complexes. Complexes virtually disappeared in all responders. Only small changes were found in total IgG or IgM levels and the reduction of IgA levels was moderate, except for one case who developed IgA deficiency. The importance of further analysis of non-responders is stressed.

Arthritis, Rheumatoid↗
PubMed1993

The CD19 signal transduction complex of B lymphocytes. Deletion of the CD19 cytoplasmic domain alters signal transduction but not complex formation with TAPA-1 and Leu 13.

CD19 expressed on the surface of B lymphocytes is a key member of a cell surface signal transduction complex that includes TAPA-1, Leu 13 and CD21. The human CD19 protein is composed of 540 amino acids with a cytoplasmic domain of 242 amino acids. Although the cytoplasmic domain of CD19 has no sequence homology with other proteins, the cytoplasmic domain of human, mouse, and guinea pig CD19 is highly conserved suggesting that this region of CD19 is at least partially responsible for signaling activity. In this study, the regions of CD19 required for intermolecular associations and signal transduction were determined by comparing a series of carboxyl-terminal cytoplasmic tail deletion mutants and a CD19/L-selectin chimera with native CD19. CD19 expressed in the human Rex T cell line and the K562 erythroleukemia cell line generated transmembrane signals and also associated with endogenous TAPA-1. Deletion of 95% of the CD19 cytoplasmic domain did not affect the ability of CD19 to be expressed or to associate with TAPA-1. However, replacement of the CD19 transmembrane and cytoplasmic domains with those of L-selectin (CD19-LAM) resulted in the loss of CD19 complex formation, suggesting that the membrane spanning domain is critical for this association. Similarly, the induction of homotypic adhesion through CD19 or truncated CD19 was equivalent, whereas homotypic adhesion was not induced via the CD19-LAM chimera. In addition, the cytoplasmic domain was not necessary for CD19 mAb-mediated growth inhibition or internalization. In contrast, the CD19 cytoplasmic domain was required for optimal mAb-induced increases in [Ca2+]i in CD19 cDNA-transfected Rex cells. Thus, the CD19 cytoplasmic domain is responsible for the induction of increased [Ca2+]i, and the transmembrane region is required for cell surface associations with the other members of the CD19 complex and most signaling events. Therefore, mAb binding to CD19 is likely to initiate multiple intracellular signal transduction cascades either through CD19 directly, or through other members of the CD19 complex.

Antigens, CD↗
PubMed1979

Experimental glomerular lesions induced by chronic immune complex formation. I. Formation and elimination of the immune complex (relationship between the immune status and the glomerular changes).

Chronic immune complex formation was induced in rabbits by daily administration of 12.5 g bovine serum. In good antibody producer animals immediate immune complex production and elimination from the circulation were demonstrable. This was followed within a few minutes by the appearance of free 125I in fairly large amounts in blood, as a sign of immediate phagocytosis and disintegration of the 125I-labelled immune complexes. Phagocytic activity decreased in the host animal during chronic heteroprotein administration in every case. The earliest glomerular changes were those of exudative glomerulonephritis, the extent of which depended on the antibody productivity of the animal. Persistent immunocomplexaemia induced by administration of the antigen over 60 and 100 days, respectively, resulted in mesangioproliferative glomerulonephritis in 7, in membranoproliferative glomerulonephritis in 3, and in membraneous glomerulonephritis in 1 out of 11 laboratory animals.

Animals↗
PubMed1994

20 S proteasomes are assembled via distinct precursor complexes. Processing of LMP2 and LMP7 proproteins takes place in 13-16 S preproteasome complexes.

The non-essential mouse proteasome beta-type subunits LMP2 and LMP7 are thought to connect proteasomes to the MHC class I antigen processing pathway. Both subunits are synthesized as proproteins. We have studied the processing of both subunits, correlated with the maturation of 20 S proteasomes in mouse T cells. Our data show that proteasome assembly occurs via 13-16 S precursor complexes which possess a protein pattern distinct from that of 20 S proteasomes. Both LMP2 and LMP7 proproteins are processed within these preproteasome complexes and only their processed forms become part of active 20 S proteasomes. Our data show that the maturation and assembly of 20 S proteasomes via precursor particles is a translation-dependent gradual process, that processing of subunit proproteins takes place in these 13-16 S complexes and that subunit processing and proteasome formation occur together.

Animals↗
PubMed2002

FTIR spectra and normal-mode analysis of a tetranuclear manganese adamantane-like complex in two electrochemically prepared oxidation states: relevance to the oxygen-evolving complex of photosystem II.

The IR spectra and normal-mode analysis of the adamantane-like compound [Mn(4)O(6)(bpea)(4)](n+) (bpea = N,N-bis(2-pyridylmethyl)ethylamine) in two oxidation states, Mn(IV)(4) and Mn(III)Mn(IV)(3), that are relevant to the oxygen-evolving complex of photosystem II are presented. Mn-O vibrational modes are identified with isotopic exchange, (16)O-->(18)O, of the mono-micro-oxo bridging atoms in the complex. IR spectra of the Mn(III)Mn(IV)(3) species are obtained by electrochemical reduction of the Mn(IV)(4) species using a spectroelectrochemical cell, based on attenuated total reflection [Visser, H.; et al. Anal. Chem. 2001, 73, 4374-4378]. A novel method of subtraction is used to reduce background contributions from solvent and ligand modes, and the difference and double-difference spectra are used in identifying Mn-O bridging modes that are sensitive to oxidation state change. Two strong IR bands are observed for the Mn(IV)(4) species at 745 and 707 cm(-1), and a weaker band is observed at 510 cm(-1). Upon reduction, the Mn(III)Mn(IV)(3) species exhibits two strong IR bands at 745 and 680 cm(-1), and several weaker bands are observed in the 510-425 cm(-1) range. A normal-mode analysis is performed to assign all the relevant bridging modes in the oxidized Mn(IV)(4) and reduced Mn(III)Mn(IV)(3) species. The calculated force constants for the Mn(IV)(4) species are f(r)(IV)= 3.15 mdyn/A, f(rOr) = 0.55 mdyn/A, and f(rMnr) = 0.20 mdyn/A. The force constants for the Mn(III)Mn(IV)(3) species are f(r)(IV)= 3.10 mdyn/A, f(r)(III)= 2.45 mdyn/A, f(rOr) = 0.40 mdyn/A, and f(rMnr) = 0.15 mdyn/A. This study provides insights for the identification of Mn-O modes in the IR spectra of the photosynthetic oxygen-evolving complex during its catalytic cycle.

Adamantane↗
PubMed1999

Comparison of the cytochrome bc1 complex with the anticipated structure of the cytochrome b6f complex: Le plus ça change le plus c'est la même chose.

Structural alignment of the integral cytochrome b6-SU IV subunits with the solved structure of the mitochondrial bc1 complex shows a pronounced asymmetry. There is a much higher homology on the p-side of the membrane, suggesting a similarity in the mechanisms of intramembrane and interfacial electron and proton transfer on the p-side, but not necessarily on the n-side. Structural differences between the bc1 and b6f complexes appear to be larger the farther the domain or subunit is removed from the membrane core, with extreme differences between cytochromes c1 and f. A special role for the dimer may involve electron sharing between the two hemes b(p), which is indicated as a probable event by calculations of relative rate constants for intramonomer heme b(p) --> heme b(n), or intermonomer heme b(p) --> heme b(p) electron transfer. The long-standing observation of flash-induced oxidation of only approximately 0.5 of the chemical content of cyt f may be partly a consequence of the statistical population of ISP bound to cytfon the dimer. It is proposed that the p-side domain of cyt f is positioned with its long axis parallel to the membrane surface in order to: (i) allow its large and small domains to carry out the functions of cyt c1 and suVIII, respectively, of the bc1 complex, and (ii) provide maximum dielectric continuity with the membrane. (iii) This position would also allow the internal water chain ("proton wire") of cyt f to serve as the p-side exit port for an intramembrane H+ transfer chain that would deprotonate the semiquinol located in the myxothiazol/MOA-stilbene pocket near heme b(p). A hypothesis is presented for the identity of the amino acid residues in this chain.

Animals↗
PubMed1997

ADP-regulation of mitochondrial free radical production is different with complex I- or complex II-linked substrates: implications for the exercise paradox and brain hypermetabolism.

In agreement with classic studies, succinate-supplemented rat and pigeon heart and nonsynaptic brain mitochondrial free radical production is stopped by ADP additions causing the stimulation of respiration from State 4 to State 3. Nevertheless, with Complex I-linked substrates, mitochondria produce free radicals in State 3 at rates similar or somewhat higher than during resting respiration. The absence of sharp increases in free radical production during intense respiration is possible due to strong decreases of free radical leak in State 3. The results indicate that Complex I is the main mitochondrial free radical generator in State 3, adding to its already known important generation of active oxygen species in State 4. The observed rate of mitochondrial free radical production with Complex I-linked substrates in the active State 3 can help to explain two paradoxes: (a) the lack of massive muscle oxidative damage and shortening of life span due to exercise, in spite of up to 23-fold increases of oxygen consumption together with the very low levels of antioxidants present in heart, skeletal muscle, and brain; (b) the presence of some degree of oxidative stress during exercise and hyperactivity in spite of the stop of mitochondrial free radical production by ADP with succinate as substrate.

Adenosine Diphosphate↗