Localized linear IgA disease and platelet abnormalities.
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Adult↗
Biomedical subjects
C Condon
Publications and source records attributed to C Condon.
Rapid production of a panel of blood group A-active oligosaccharides using chemically synthesized di- and tri-saccharide primers and an easily prepared porcine (1-->3)-alpha-N-acetyl-D-galactosaminyltransferase.
A porcine (1-->3)-alpha-N-acetyl-D-galactosaminyltransferase was obtained in a state suitable for preparative-scale (mg-scale) synthesis using simple procedures requiring only three days of effort. The enzyme thus prepared transferred GalNAc efficiently from UDP-GalNAc to six different chemically synthesized di- and tri-saccharide H-active structures to yield blood-group A-active oligosaccharides that were characterized by 1H NMR spectroscopy and mass spectrometry. This work further demonstrates the efficiency and attractiveness of using glycosyltransferases in a combined chemoenzymatic approach for the rapid production of biologically active oligosaccharides.
ABO Blood-Group System↗
Ribosomal RNA antitermination in vitro: requirement for Nus factors and one or more unidentified cellular components.
Using an in vitro transcription assay, we have successfully demonstrated read through of a Rho-dependent terminator by the ribosomal RNA antitermination system. The assay used a DNA template containing a promoter-antiterminator-terminator arrangement, RNA polymerase, termination factor Rho, antitermination factors NusA, NusB, NusE, and NusG, and a cellular extract depleted of NusB. Terminator read-through was highly efficient only in the presence of the extract and Nus factors, suggesting that an as yet uncharacterized cellular component is required for ribosomal antitermination. The NusB-depleted extract had no activity in the absence of NusB, confirming an absolute requirement for this protein in ribosomal RNA antitermination. The DNA template requirements were the same as those previously established in vivo; transcription of a wild-type boxA sequence is both necessary and sufficient to promote RNA polymerase modification into a terminator-resistant form.
Bacterial Proteins↗
Depletion of functional ribosomal RNA operons in Escherichia coli causes increased expression of the remaining intact copies.
The synthesis of ribosomal RNA is a complex and highly regulated process. To study this process, we have used deletion-insertions to disrupt sequentially from one to four of the seven rRNA (rrn) operons on the Escherichia coli genome. Inactivation of four rrn operons caused a 2.3-fold increase in the expression of a chloramphenicol acetyl transferase reporter gene fused to the tandem promoters of rrnA and a similar increase in the expression of the trp tRNA gene at the end of rrnC. This reflected enhanced expression of the remaining operons to compensate for having only three intact copies. The elevated expression was caused by an increase in both transcription initiation and RNA polymerase elongation rates specifically on rrn operons and occurred in the absence of changes in the intracellular concentration of ppGpp, suggesting that ppGpp is not involved in the regulation of this phenomenon. We discuss these results in relation to the ribosome feedback inhibition model described by Nomura and coworkers.
Base Sequence↗
Comparison of the expression of the seven ribosomal RNA operons in Escherichia coli.
We have compared the expression of the seven ribosomal RNA operons (rrn) of Escherichia coli and their responses to a variety of physiological and genetic perturbations. We used a set of rrn promoter fusion constructs in their native chromosomal positions to examine effects of chromosomal location on rrn operon expression and the same set of fusions on lambda lysogens to assay intrinsic promoter strengths independent of chromosome context. In its native chromosomal location, expression of the rrnH operon was significantly lower than expected. This effect was not attributable to weak promoter activity and was dependent on the growth medium. The rrnE operon had reduced promoter activity relative to the other ribosomal operons in minimal medium and thus appears to have abnormal growth rate regulation. The ribosomal RNA operons showed varied responses to amino acid starvation; expression of rrnD was inhibited most. There was only a slight increase in rrn transcription in response to a temperature shift (30 degrees C to 42 degrees C) and the differences between individual operons was very small. The rrnG operon showed a significantly lower response than the other ribosomal RNA operons to a depletion of the rrn transcription activator, Fis, and thus appears to have decreased Fis-mediated transactivation. Finally, the chromosomal fusion strains were used to study the effect on growth rate of inactivating each rrn operon. In fast growth conditions, loss of certain rrn operons caused subtle decreases in growth rate on complex medium.
Base Sequence↗
Use of restriction fragment length polymorphisms resolved by pulsed-field gel electrophoresis for subspecies identification of mycobacteria in the Mycobacterium avium complex and for isolation of DNA probes.
Mycobacterial strains from the Mycobacterium avium complex were compared with each other and with Mycobacterium phlei isolates by restriction endonuclease digestion of chromosomal DNA with SspI and analysis by pulsed-field gel electrophoresis. Characteristic profiles were observed for known typed strains, and five groups were identified. Primary bovine isolates identified as Mycobacterium paratuberculosis by classical methods were shown to fall into both the M. paratuberculosis- and M. avium-like groups. M. paratuberculosis 18 was in the latter category. Two Mycobacterium intracellulare strains of different Schaefer serotypes had different digestion profiles. In addition, this system was exploited for the preparation of DNA probes by the isolation, digestion, and subcloning of DNA fragments separated by pulsed-field gel electrophoresis. Probe JC12 hybridized only to M. avium complex strains, but not to M. phlei, showing characteristic hybridization profiles for each of the groups previously identified by pulsed-field gel electrophoresis. The approach taken in the study lends itself to the comparative analysis of members of the M. avium complex and to the isolation and characterization of DNA probes with specificity for these mycobacteria.
DNA Probes↗
A retrospective study of myocardial infarction occurring in elderly patients in a coronary care unit.
Myocardial infarction is a major cause of morbidity and mortality particularly in the elderly. Coronary Care Unit monitoring has resulted in the improvement in prognosis in all age groups. In this study, the clinical course and outcome of 204 consecutive patients with acute myocardial infarction aged over 65 years is retrospectively analysed. All patients were managed in a Coronary Care Unit operating a needs related policy. Those under 75 years (120 patients) were compared to those over that age (84 patients). The groups differed in terms of clinical presentation, cardiac enzymatic rise and response to drug therapy. However they had similar complication rates, morbidity and mortality.
Age Factors↗
Fumarate reductase of Escherichia coli: an investigation of function and assembly using in vivo complementation.
Recombinant plasmids which carried portions of the Escherichia coli frd operon were constructed and their expression examined by in vivo complementation of E. coli MI1443. This strain lacked a chromosomal frd operon and was unable to grow anaerobically on glycerol and fumarate. Introduction of all four fumarate reductase subunits into E. coli MI1443 was essential for the restoration of growth. The FRD A, FRD B dimer (but neither subunit alone) was active in the benzyl viologen oxidase assay. Both FRD C and FRD D were required for membrane association of fumarate reductase and for the oxidation of reduced quinone analogues. Introduction into E. coli MI1443 of the frdABC and frdD genes on two separate plasmid vectors failed to restore anaerobic growth on glycerol and fumarate. Thus separation of the DNA coding for the FRD C and FRD D proteins affected the ability of fumarate reductase to assemble into a functional complex.
Anaerobiosis↗
Epithelial responses evoked by stimulation of submucosal neurons in guinea pig distal colon.
The influence of submucosal neurons on ion transport in the guinea pig distal colon was examined in muscle-stripped sheets of submucosa-mucosa set up in Ussing flux chambers. Spontaneous variations in potential differences (PD) and short-circuit current occurred ranging from positive currents associated with luminal negative PDs to negative currents with luminal positive PDs. Basal current in both groups was reduced by mucosal amiloride. In tissues with positive or negative short-circuit currents, unidirectional mucosal-to-serosal sodium fluxes were greater than serosal-to-mucosal fluxes and small net absorptive fluxes were present. Little or no chloride secretory flux was present. Electrical stimulation of submucosal neurons evoked a tetrodotoxin-sensitive increase in short-circuit current in tissues with positive or negative short-circuit currents. This was due to an increase in net chloride flux and little change in net sodium flux or residual flux. The increase in net chloride flux was due almost entirely to an increase in serosal-to-mucosal chloride flux and was associated with an increase in total tissue conductance. The stimulus-evoked response was reduced by atropine. These results suggest that stimulation of submucosal neurons that innervate the distal colonic epithelium evokes a large chloride secretory response that is due in part to release of acetylcholine at neuro-enterocyte junctions.
Amiloride↗
A mutant of Escherichia coli fumarate reductase decoupled from electron transport.
The terminal electron-transfer enzyme fumarate reductase of Escherichia coli is a complex iron-sulfur flavoenzyme composed of four nonidentical subunits organized into two domains: FrdA and -B (a membrane-extrinsic catalytic domain) and FrdC and -D (a transmembrane anchor domain). We have identified a mutation within the membrane-intrinsic domain that alters the electron transfer properties of the iron-sulfur and flavin redox centers of the catalytic domain. Functional electron flow from the quinone analog 2,3-dimethyl-1,4-naphthoquinone or from the electron transport chain is impaired. However, the mutant enzyme can be reduced normally by single-electron donors such as the dye benzyl viologen. The mutant phenotype results from a single A----G transition changing His-82, within the second transmembrane alpha-helix of the FrdC anchor sequence, to an arginine. The mutation, physically located within the anchor domain, is manifested by altered catalytic properties, indicating that the intrinsic and extrinsic domains are conformationally connected. These results confirm the important role of the anchor subunits in functional electron transport and have implications for communication between intrinsic and extrinsic domains of membrane proteins.
Base Sequence↗
The succinate dehydrogenase of Escherichia coli. Immunochemical resolution and biophysical characterization of a 4-subunit enzyme complex.
Using EPR spectroscopy to monitor the integrity of the enzyme, conditions have been established which allow specific immunoprecipitation of the succinate dehydrogenase complex of Escherichia coli. The enzyme complex precipitated from Lubrol PX-solubilized membranes by monospecific antiserum in the presence of a cocktail of protease inhibitors contains four polypeptides of apparent MrS 71,000, 26,000, 17,000, and 15,000. The 71-kDa flavopeptide is readily susceptible to proteolysis, and the enzyme complex shows unusual facile dissociation. Spectroscopic measurements indicate the presence of a [2Fe-2S] cluster (Center 1), a [3Fe-xS] cluster (Center 3), and a b-type cytochrome. In addition, a change in relaxation of Center 1 at low potentials is indicative of Center 2. Midpoint redox potentials of Centers 1-3 for both the membrane-bound and detergent-solubilized enzyme were estimated to be +10 mV, -175 mV, and +65 mV, respectively.
Antigen-Antibody Complex↗
Molecular biology, biochemistry and bioenergetics of fumarate reductase, a complex membrane-bound iron-sulfur flavoenzyme of Escherichia coli.
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Amino Acid Sequence↗