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Biomedical subjects

D H Bing

Publications and source records attributed to D H Bing.

At least 19 recordsLinked to original sources
PubMed1990

Synthesis of the third component of complement (C3) by lectin-activated and HTLV-infected human T-cells.

The third component of complement (C3) plays key roles in complement activation of both the classical and alternative pathways. The liver is the major site of C3 synthesis; monocytes, B-lymphocytes and leukemic cell lines of the myeloid lineage also synthesize C3. Here we report that the C3 gene is inactive in fresh T-cells, but active in T-cells treated with the lectin phytohemagglutinin (PHA). Northern blot hybridization studies show that PHA-activated T-cells and all the T-cell lines tested express the 5.3 kb RNA transcript reported for C3 in HepG2, a hepatoma cell line, and monocytes. We used radioimmune precipitation followed by polyacrylamide gel electrophoresis to show that PHA-stimulated T-cells and T-cell lines, which are not infected with the human T-lymphotropic virus (HTLV), synthesize and release C3 proteins with molecular masses of 185, 115 and 80 kD; HTLV-infected T-cell lines release C3 proteins of 170, 115 and 70 kD. In contrast, monocytes produced C3 proteins of 115 and 70 kD similar to the serum form of this protein. The role of T-lymphocyte C3 and the implications of HTLV-infection are discussed.

Blotting, Northern↗
PubMed1989

Factor J: isolation and characterization of a new polypeptide inhibitor of complement C1.

An Mr 20,000 protein inhibitor of C1, the first component of complement, has been purified from human urine and characterized. This inhibitor, tentatively designated factor J, is apparently distinct from known complement inhibitors. During purification on QAE-Sephadex, Mono Q, and heparin-Sepharose, factor J was detected by its ability to inhibit the complement-mediated lysis of sheep erythrocytes bearing antibody, C1, and activated C4 (EAC14). The purity of factor J was documented by the concordant elution from a hydroxylapatite column of functional activity and the UV absorbance as measured at three different wavelengths (220, 254, and 280 nm). The relative Mr of 20,000 was determined by sodium dodecyl sulfate-slab gel electrophoresis of radioiodinated protein. Amino acid analysis indicated a high cysteine content and allowed calculations of a specific activity of 7 functional units/pmol. The target of factor J inhibitory activity on the lysis of EAC14 was localized to C1 by the following criteria: factor J inhibited C1 in a C1 transfer assay, but had no effect on C42 activity or decay, and had no effect on the efficiency of isolated C2 or C3-C9 as provided in serum-EDTA. Factor J inhibition was rapid and not significantly influenced by temperature. In a second functional assay, factor J inhibited the association of the tetrameric complex C1r2s2 with 125I-C1q, and the results, when analyzed graphically by a reciprocal plot, were consistent with noncompetitive inhibition (Ki = 529-760 pM range). Functional and/or antigenic data indicated that factor J is distinct from the other known inhibitors of C1, namely the C1 inhibitor and the C1q inhibitor. Antihuman serum precipitated radioiodinated factor J, indicating that an antigen identical or cross-reacting with factor J exists in serum. In summary, factor J is a newly described potent inhibitor of C1 function.

Animals↗
PubMed1987

Transcriptional regulation of genes encoding the acute-phase proteins CRP, SAA, and C3.

Inflammation or acute tissue injury results in a programmed change in the concentration of several plasma proteins. Among these proteins, two--C-reactive protein (CRP) and serum amyloid A protein (SAA)--increase up to 1000-fold after an acute-phase stimulus in humans and rabbits. To determine the mechanism for regulation of acute-phase gene expression, we examined changes in the rates of transcription and specific hepatic mRNA content for rabbit CRP, SAA, and some complement protein mRNA during an acute-phase response. Induction of a sterile inflammatory reaction with intramuscular injection of turpentine resulted in an increase in the hepatocellular content of CRP, SAA, C3, and factor B mRNA and the transcription of CRP, SAA, and C3 genes. These data suggest that the increase in CRP, SAA, and C3 serum concentrations observed during an acute-phase reaction is due to an increase in biosynthesis and is, at least in part, under transcriptional control.

Acute-Phase Proteins↗
PubMed1987

Amelioration of immune complex-mediated glomerulonephritis by synthetic protease inhibitors.

Proteases are involved in the pathogenesis of inflammatory diseases by participating in the activation of mediator systems and by producing proteolytic tissue injury. Homeostatic control of inflammation is accomplished in part by physiologic protease inhibitors. The authors investigated the effectiveness of a number of synthetic protease inhibitors in ameliorating the glomerular injury induced by immune complex-mediated glomerulonephritis in mice. Two amidine-type protease inhibitors, bis (5-amidino-2-benzimidazolyl)methane and 1,2-bis (5-amidino-2-benzimidazolyl)ethane, had the greatest effects. They caused a marked reduction in glomerular necrosis (P less than 0.001) but did not affect the amount or site of immune complex localization or leukocyte influx. The inhibition constants of the protease inhibitors against nine purified physiologic proteases were determined. These results were discussed in relation to the effectiveness of the protease inhibitors in reducing glomerular injury. This investigation indicates that the administration of synthetic protease inhibitors can have a beneficial effect on immune-mediated inflammatory injury.

Amidines↗
PubMed1987

Interactions of plasma kallikrein and C1-s with normal and dysfunctional C1(-)-inhibitor proteins from patients with hereditary angioneurotic edema: analytic gel studies.

Purified preparations of normal C1(-)-inhibitor (C1(-)-INH) formed high mol wt complexes with plasma kallikrein that were stable during sodium dodecyl sulfate (SDS)-gel electrophoresis, but most of the dysfunctional C1(-)-INH proteins isolated from plasma of patients with type II hereditary angioneurotic edema (HANE) did not. Two of eight dysfunctional C1(-)-INH proteins were cleaved to lower mol wt forms that were not seen following the reaction of normal C1(-)-INH with equimolar amounts, or less, of plasma kallikrein. Only the higher mol wt component of normal C1(-)-INH (106,000 mol wt) appeared to form a stable complex with the plasma kallikrein, whereas both the 106,000 and 96,000 mol wt forms made stable complexes with C1-s. When a preparation of normal C1(-)-INH containing a homogeneous single band of C1(-)-INH was exposed to C1-s or kallikrein, a "doublet" form evolved in which the heaviest band was in the original position of native C1(-)-INH; C1-s cleavage provided a second band of 96,000; and cleavage by kallikrein, a second band of 94,000 mol wt. We conclude that dysfunctional C1(-)-INH proteins from plasma of persons with type II hereditary angioneurotic edema have impaired interactions with plasma kallikrein and are heterogeneous with respect to these interactions. Moreover, the requirements for the formation of stable complexes between normal C1(-)-INH and plasma kallikrein differed from those for stable complex formation with C1-s. The doublet form of C1(-)-INH, which purified preparations frequently demonstrate, may be due to prior cleavage by C1-s or kallikrein.

Angioedema↗
PubMed1986

Thrombin active-site regions.

Knowledge is being gained about topographic features of alpha-thrombin and how they may define thrombin specificity and biologic functions. Thrombin is not just an enzyme with moderately restricted proteolytic capabilities, yet with extraordinarily high specificities for certain bonds (such as the A alpha-cleavage site in fibrinogen), but also is a protein with hormonelike activities involving cell receptor interactions. Such activities do not require the catalytically active enzyme, but are blocked by hirudin (also antithrombin III). These appear to involve an unique insertion and subsequent peptide segment at an exon junction. On the other hand, the enzymic functions of thrombin depend on the catalytic site, per se, and derive specificity from the adjacent apolar-binding site within the fibrinopeptide side and the independent anionic-binding site within the fibrin side of the active groove.

Amino Acid Sequence↗
PubMed1986

Structure-function relationships of thrombin based on the computer-generated three-dimensional model of the B chain of bovine thrombin.

The advent of sophisticated computer graphics systems that permit the representation of macromolecular structure has made it possible to examine protein structure in detail. We have used one aspect of this technology to develop a model of thrombin. The model is based on structural and functional similarities this enzyme exhibits with respect to proteins found in the family of serine proteinases. This review has covered interpretations of the structure of the model based on analyses of data that had been collected before and after the model was developed. On one hand, the conceptualization of primary and secondary features in the model of the active site of thrombin has for the most part been preceded by data from experiments on the interaction of thrombin with naturally occurring substrates and inhibitors. The features of the model explain these data adequately. On the other hand, the model has been more recently used in an interactive way to derive information about the bioregulatory aspects of thrombin. The realization that the amino-terminus portion of the cyanogen-bromide fragment was probably not part of the chemotactic activity, because it was probably internalized in the native protein, has suggested that synthetic analogs should focus more on the carboxyterminus of the peptide. It is hoped that in the future the model will continue to serve more in this function and that it can be used to explore further other aspects about the structural and functional relationships of this enzyme.

Amino Acid Sequence↗
PubMed1985

Variability in purified dysfunctional C1(-)-inhibitor proteins from patients with hereditary angioneurotic edema. Functional and analytical gel studies.

C1(-)-inhibitor (C1(-)-INH) proteins from normal persons and members of eight different kindred with dysfunctional C1(-)-INH proteins associated with hereditary angioneurotic edema (HANE) were compared with respect to their inhibitory activity against purified preparations of C1s-, plasma kallikrein, activated forms of Hageman factor, and plasmin. Each dysfunctional C1(-)-INH protein showed a unique spectrum of inhibitory activity against these enzymes. Although none of the dysfunctional C1(-)-INH proteins significantly impaired amidolysis by plasmin, all but one inhibited activated Hageman factor. One purified dysfunctional C1(-)-INH (Ta) inhibited purified C1s- to a normal degree. Another C1(-)-INH (Za) had almost seven times as much inhibitory activity as normal C1(-)-INH against activated Hageman factor, but had decreased activity against C1s- and no activity against plasmin. Analyses of mixtures of plasmin and C1(-)-INH proteins in SDS gel electrophoresis revealed variability in the patterns of complex formation and cleavage of dysfunctional proteins after exposure to C1s- and plasmin. Some bound to plasmin and were cleaved, even though none significantly impaired the amidolytic activity of plasmin. Two were cleaved by C1s-, whereas neither normal or other dysfunctional C1(-)-INH were cleaved. Dysfunctional C1(-)-INH proteins from patients with HANE are thus heterogeneous in their inhibitory properties and there must be different structural requirements for the inhibition of the various plasma enzymes that can be regulated by normal C1(-)-INH. The data suggest that in addition to common sites of interactions between these proteases and C1(-)-INH, there are also points of contact that are specific for each protease. Genetic mutations leading to structural changes at some of these sites may have differing effects on the interaction between individual proteases and abnormal C1(-)-INH proteins. These alterations may allow these proteins to serve as probes for structural requirements for inhibitory actions of normal C1(-)-INH.

Angioedema↗
PubMed1978

The first component of complement. A quantitative comparison of its biosynthesis in culture by human epithelial and mesenchymal cells.

Epithelial and mesenchymal cells synthesized and secreted all three subcomponents of the first component of complement (C1): C1q, C1r, and C1s. Quantitatively, however, columnar and transitional epithelial cells secreted 400--3,700 times more hemolytically active C1 than monocytes or fibroblasts. Only columnar epithelial cells synthesized C1 subcomponents with subunit structures similar to their serum counterparts. Transitional epithelial cells, fibroblasts, and monocytes produced C1q and C1s with subunits of apparent molecular weights larger than reported values. C1r from all cell lines was physiochemically similar to serum C1r.

Cells, Cultured↗
PubMed1978

Inhibition of four human serine proteases by substituted benzamidines.

A series of substituted benzamidines has been examined for their inhibitory activity against the human serine proteases--trypsin, thrombin, plasmin, and C1s, a subunit of the first component of complement. The inhibition constants obtained for each enzyme were correlated with physical-chemical properties of the substituent group using the quantitative structure-activity relationship approach. This analysis indicated that plasmin and C1s are very similar in their interactions with substituted benzamidines. The binding of benzamidines in both enzymes was affected by electron donation from the substituent and its hydrophobicity. Thrombin-benzamidine interaction was affected only by the hydrophobicity of the substituent. Trypsin displayed a complex interaction with substituted benzamidines, and interaction was dependent on molar refractivity and molecular weight. Certain substituents deviated significantly from the interactions predicted by the analysis. These compounds, the (m- and p-amidinophenyl)pyruvic acids, when analyzed by computer modeling, suggested that direct interaction between the substituent and the enzyme surface is important in assessing the effect of substituent groups on inhibitory activity.

Amidines↗
PubMed1978

Interactive computer surface graphics approach to study of the active site of bovine trypsin.

A descriptive medium for the presentation of protein structure has been developed and used to evaluate the structure of the active site of bovine trypsin (EC 3.4.21.4). This technique, involving advanced computer graphics technology, permits the facile display of a representation of the molecular surface of proteins of known structure and employs color to code the structural or chemical features of this surface. Benzamidine derivatives were inserted into the benzamidine-binding site of trypsin and the binary inhibitor-trypsin complex was evaluated by using the computer-generated structure. On the basis of qualitative assessments of the contribution of electrostatic and hydrophobic forces to the binding energy associated with complex formation, we made predictions concerning the effects of interaction of benzamidine substituents and amino acid side chains upon the binding energy associated with inhibitor-protein binding. The computer display of the molecular surfaces of the binary complex of substituted benzamidines and trypsin permitted unique insight into the identity and chemical properties of the atoms that participate at the interface of the molecular surfaces of the inhibitor and the protein. The computer-generated molecular surface display can potentially be combined with quantitative definition of the physical forces involved in the interaction of molecular surfaces. This technology should facilitate the study of the structure-activity relationship of substrates, inhibitors, and drugs that bind to proteins of known three-dimensional structure.

Animals↗
PubMed1977

Inhibition of C1s-induced vascular leakage in guinea pigs by substituted benzamidine and pyridinium compounds.

A variety of benzamidine and pyridinium compounds were examined for their ability to inhibit irreversibly C1s-induced vascular leakage in guinea pig skin. Vascular leakage was compared with esterolysis of N-Z-L-Tyr-Np and catalysis of EAC42 formation by C1s. Vascular leakage correlated significantly better with esterolytic activity than with EAC42 formation. The presence of a sulfonyl fluoride moiety in the compounds is important in the inhibition of C1s-induced vascular leakage.

Amidines↗