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Biomedical subjects

D W Hough

Publications and source records attributed to D W Hough.

At least 19 recordsLinked to original sources
PubMed1992

Zinc binding by retroviral integrase.

Zinc binding by integrase from Moloney murine leukaemia virus and a protein A fusion protein containing integrase from human immunodeficiency virus type 1 was demonstrated by a zinc blotting technique using 65ZnCl2. Autoradiography revealed a clear band that was absent from the appropriate controls. This band co-migrated with the major band in Coomassie-stained gels and in immunoblots. This binding activity was retained in the presence of competing divalent cations and was sensitive to oxidation. This is the first demonstration of zinc binding by intact retroviral integrase.

Amino Acid Sequence↗
PubMed1992

Dihydrolipoamide dehydrogenase from the halophilic archaebacterium Haloferax volcanii: characterization and N-terminal sequence.

Dihydrolipoamide dehydrogenase, a flavin disulfide reductase, has been purified and characterized from Haloferax volcanii. The enzyme is a dimer of relative mass 128,000, with an optimal activity at pH 9.0 in 1 M NaCl. Following reduction with its substrate, dihydrolipoamide, the enzyme is inactivated through covalent bond formation with the trivalent arsenical p-aminophenyl arsenoxide. The amino acid composition and the amino acid sequence of the first 49 residues of the N-terminus have been determined.

Amino Acid Sequence↗
PubMed1992

The enzymology of archaebacterial pathways of central metabolism.

From a comparison of the pathways of central metabolism in the archaebacteria, eubacteria and eukaryotes, it is clear that the basic pathways were established before the divergence of the three kingdoms, but that the notable differences may provide important clues to their evolution. From these comparisons, enzymes found in all evolutionary groups have been chosen for detailed structural studies; given the range of extreme phenotypes found within the archaebacteria, these studies will be crucial to our understanding of the structural basis for protein stability and how such features may be engineered into a protein of choice.

Archaea↗
PubMed1991

Crystallization and preliminary crystallographic study of glucose dehydrogenase from the archaebacterium Thermoplasma acidophilum.

Single crystals of glucose dehydrogenase from the archaebacterium Thermoplasma acidophilum were obtained using the hanging-drop vapour diffusion method and polyethylene glycol as a precipitant in the presence of NADP+ at pH 5.4. The crystals belong to the hexagonal space group P6122 or P6522, with unit cell dimensions a = b = 121.9 angstrom, c = 229.6 angstrom and with two molecules in the asymmetric unit.

Bacterial Proteins↗
PubMed1991

Expression and purification of plasmid-encoded Thermoplasma acidophilum citrate synthase from Escherichia coli.

The citrate synthase gene from the thermophilic archaebacterium Thermoplasma acidophilum was expressed in Escherichia coli, yielding an active product of the expected molecular weight. Manipulation of the citrate synthase gene in a series of pUC19 constructs showed that the presumed Thermoplasma ribosome binding site is recognized by the E. coli ribosome. A rapid purification of the expression product to homogeneity was achieved, based on the thermostability of Thermoplasma citrate synthase.

Base Sequence↗
PubMed1990

Citrate synthase from the thermophilic archaebacterium Thermoplasma acidophilium. Cloning and sequencing of the gene.

The gene encoding the citric acid cycle enzyme, citrate synthase, has been cloned from the thermoacidophilic archaebacterium, Thermoplasma acidophilum. We report the sequencing of this gene and its flanking regions, and the derived amino acid sequence of the enzyme is compared by multiple-sequence alignment analysis with those of citrate synthases from eubacterial and eukaryotic organisms. The similarity is less than 30% between the archaebacterial and non-archaebacterial sequences, although the majority of residues implicated in the catalytic action of the enzyme have been conserved across all three kingdoms. The cloned archaebacterial gene has been expressed in Escherichia coli to produce catalytically active citrate synthase. This is the first reported sequence of citrate synthase from the archaebacteria.

Amino Acid Sequence↗
PubMed1990

Subcellular localisation of dihydrolipoamide dehydrogenase and detection of lipoic acid in bloodstream forms of Trypanosoma brucei.

In the long-slender bloodstream form of Trypanosoma brucei, the enzyme dihydrolipoamide dehydrogenase exists in the absence of the 2-oxo-acid dehydrogenase complexes of which it is normally a component, and appears to be associated with the plasma membrane of the organism [Danson, M. J., Conroy, K., McQuattie, A. & Stevenson, K. J. (1987) Biochem. J. 243, 661-665]. In the present paper, a complete subcellular fractionation of T. brucei has been carried out and, by comparison with marker enzymes, it is confirmed that the dihydrolipoamide dehydrogenase is indeed associated with the plasma membrane. In addition, we now provide evidence that the distribution of the enzyme is over the whole surface of the membrane, including the flagellar pocket region, and that the enzyme is not found in any other cellular fraction. A study of the latency of the enzyme suggests that it is located on the cytoplasmic surface of the plasma membrane. The discovery of the presumed substrate of dihydrolipoamide dehydrogenase, lipoic acid, is reported for T. brucei. Using a biological assay involving a strain of Escherichia coli that requires lipoic acid for growth, we have found that acid-hydrolysed extracts of T. brucei contain 1.7 (+/- 0.2) ng of the cofactor/mg protein. The chemical nature of the lipoic acid was confirmed by gas chromatography/mass spectrometry.

Animals↗
PubMed1989

Purification and characterization of glucose dehydrogenase from the thermoacidophilic archaebacterium Thermoplasma acidophilum.

Glucose dehydrogenase was purified to homogeneity from the thermoacidophilic archaebacterium Thermoplasma acidophilum. The enzyme is a tetramer of polypeptide chain Mr 38,000 +/- 3000, it is catalytically active with both NAD+ and NADP+ cofactors, and it is thermostable and remarkably resistant to a variety of organic solvents. The amino acid composition was determined and compared with those of the glucose dehydrogenases from the archaebacterium Sulfolobus solfataricus and the eubacteria Bacillus subtilis and Bacillus megaterium. The N-terminal amino acid sequence of the Thermoplasma acidophilum enzyme was determined to be: (S/T)-E-Q-K-A-I-V-T-D-A-P-K-G-G-V-K-Y-T-T-I-D-M-P-E.

Amino Acid Sequence↗
PubMed1989

Sequence alignment of citrate synthase proteins using a multiple sequence alignment algorithm and multiple scoring matrices.

The alignment of Escherichia coli citrate synthase to pig heart citrate synthase and the multiple alignment of the known sequences of the citrate synthase family of enzymes have been performed using six different amino acid similarity scoring matrices and a large range of gap penalty ratios for insertions and deletions of amino acids. The alignment studies have been performed as the first step in a project aimed at homology modelling E. coli citrate synthase (a hexamer) from pig heart citrate synthase (a dimer) in a molecular modelling approach to the study of multi-subunit enzymes. The effects of several important variables in producing realistic alignments have been investigated. The difference between multiple alignment of the family of enzymes versus simple pairwise alignment of the pig heart and E. coli proteins was explored. The effects of initial separate multiple alignments of the most highly related or most homologous species of the family of enzymes upon a subsequent pairwise alignment between species was evaluated. The value of 'fingerprinting' certain residues to bias the alignment in favour of matching those residues, as well as the worth of the computerized approach compared to an intuitive alignment technique, were assessed.

Algorithms↗
PubMed1986

The efficient production of stable, human monoclonal antibody-secreting hybridomas from EBV-transformed lymphocytes using the mouse myeloma X63-Ag8.653 as a fusion partner.

The mouse myeloma X63-Ag8.653 was fused to peripheral blood lymphocytes (PBL) from apparently healthy individuals, autoimmune patients and volunteers immunised with Rhesus (D) positive erythrocytes. Fusions were performed with or without prior transformation of PBL with Epstein-Barr virus (EBV). Using untransformed PBL, under the best conditions a mean fusion frequency of 8.4 X 10(-6) was obtained, with 22% of the resulting hybridomas secreting human immunoglobulin. Fusions with EBV-transformed cells gave fusion frequencies of 1.0 X 10(-4), with 85-90% of hybridomas secreting human immunoglobulin. The heterohybridomas formed in both cases cloned efficiently and had doubling times of 24-30 h. The heterohybridomas secreted human IgM, IgG and IgA of both kappa and lambda isotypes and culture supernatants contained up to 50 micrograms ml-1 of human immunoglobulin. Mouse immunoglobulin was not detected in the culture supernatants. 28 hybrids were selected for vigorous growth and antibody production by repeated cloning. Immunoglobulin synthesis was stabilised in 26 of these hybridomas after two or three cloning steps. The heterohybridomas have been successfully grown in large volumes for periods up to 15 months. It is concluded that the mouse myeloma X63-Ag8.653 is a suitable fusion partner with EBV-transformed B cells in the efficient production of human monoclonal antibodies.

Animals↗
PubMed1986

A comparison of ELISA screening methods for the production of monoclonal antibodies against soluble protein antigens.

A library of monoclonal antibodies against pig heart citrate synthase has been raised. Twelve solid-phase immunoassay systems, employing different methods of antigen immobilization, have been compared for their ability to detect the various members of this library. It was found that a sandwich immunoassay, in which the citrate synthase antigen was immobilized on the solid support via a polyclonal antibody preparation, was the only system capable of detecting all the monoclonal antibodies tested. It is suggested that such a sandwich assay should be used in preference to direct assays for the initial screening of monoclonal antibodies.

Antibodies, Monoclonal↗
PubMed1985

Citrate synthase: an immunochemical investigation of interspecies diversity.

Rabbit antibodies have been raised to pig heart citrate synthase. Using purified IgG, competitive enzyme-linked immunoassays and assays of citrate synthase activity indicate the presence of antibodies to a number of antigenic sites on the enzyme, only some of which are essential for catalytic activity. From a comparison of citrate synthases from prokaryotic and eukaryotic organisms, the degree of interaction between antibody and enzyme was in the order: pig heart greater than pigeon breast greater than Bacillus megaterium greater than Escherichia coli. These findings are discussed in terms of the known interspecies diversity of the enzyme.

Animals↗
PubMed1983

Heterogeneity of Fc gamma receptor expression on human cell lines.

Receptors for the Fc gamma portion of IgG (Fc gamma R) may be detected on several cell populations using a variety of assay techniques. The heterogeneity of these receptors on human cell lines has been investigated using a rabbit antiserum raised against Fc gamma R expressed on K562 cells. This reagent only partially inhibited Fc gamma R binding on K562 cells, but completely blocked that on Daudi cells. The results are compatible with the hypothesis that Daudi cells express only one form of Fc gamma R, which is similar if not identical to one of the 2 Fc gamma-binding activities detected on K562 cells. Cell lines may therefore be useful sources of different homogeneous Fc gamma R material for the development of reagents to study these receptors on cell subpopulations in health and disease.

Animals↗
PubMed1978

Further studies of immunoglobulin synthesis by guinea pig leukaemic lymphocytes.

The L2C leukaemia is a B-lymphocytic neoplasm of strain 2 guinea-pigs, maintained by passaging in vivo. It synthesizes mu and lambda immunoglobulin chains. These combines to form monomeric (7S) IgM molecules which are inserted into the plasma membranes. From here they are shed as monomeric IgM and as a species of higher molecular weight which has not been further defined. The synthesis of lambda chain is in excess of that required for the IgM molecule, the surplus being exported directly from the cell without any intervening phase in the plasma membrane. Quantitative estimates of synthetic rates and pool sizes for these immunoglobulin species are presented.

Animals↗
PubMed1977

Proteolysis of lymphocytic surface immunoglobulin.

Limited proteolysis of lymphocytic surface immunoglobulins in guinea-pig, rabbit and man was investigated by immunofluorescence using conjugated antisera specific for immunoglobulin fragments. The cell surface IgM of guinea pig L2C leukaemic lymphocytes and rabbit blood lymphocytes was cleaved in situ at its hinge region by papain. The Fcmicron fragment remained attached to the membrane and could be stained with the appropriate anti-Fc conjugate. The surface IgD and IgM of human chronic lymphocytic leukaemia cells was cleared from the cell surface by papain, as shown by reagents directed against both Fab and Fc region determinants. This could be due either to proteolytic degradation of membrane bound Fc or to initial cleavage of Ig from the membrane at some point other than the hinge region.

Animals↗