Formation of critical oligomers is a key event during conformational transition of recombinant syrian hamster prion protein

We have investigated the conformational transition and aggregation process of recombinant Syrian hamster prion protein (SHaPrP90-232) by Fourier transform infrared spectroscopy, circular dichroism spectroscopy, light scattering, and electron microscopy under equilibrium and kinetic conditions. SHaPrP90-232 showed an infrared absorbance spectrum typical of proteins with a predominant alpha-helical structure both at pH 7.0 and at pH 4.2 in the absence of guanidine hydrochloride. At pH 4.2 and destabilizing conditions (0.3-2 m guanidine hydrochloride), the secondary structure of SHaPrP90-232 was transformed to a strongly hydrogen-bonded, most probably intermolecularly arranged antiparallel beta-sheet structure as indicated by dominant amide I band components at 1620 and 1691 cm-1. Kinetic analysis of the transition process showed that the decrease in alpha-helical structures and the increase in beta-sheet structures occurred concomitantly according to a bimolecular reaction. However, the concentration dependence of the corresponding rate constant pointed to an apparent third order reaction. No beta-sheet structure was formed within the dead time (190 ms) of the infrared experiments. Light scattering measurements revealed that the structural transition of SHaPrP90-232 was accompanied by formation of oligomers, whose size was linearly dependent on protein concentration. Extrapolation to zero protein concentration yielded octamers as the smallest oligomers, which are considered as "critical oligomers." The small oligomers showed spherical and annular shapes in electron micrographs. Critical oligomers seem to play a key role during the transition and aggregation process of SHaPrP90-232. A new model for the structural transition and aggregation process of the prion protein is described.     

Bioaugmentation strategies for remediating mixed chemical effluents

Operationally exhausted metal working fluids are chemically mixed, produced in large quantities (400 000 tonnes year in the U.K.), and potentially environmentally toxic. It is essential to develop more reliable and economical approaches for their disposal. We investigated the effectiveness of a defined bacterial consortium, constructed specifically for treating metal-working fluid (MWF), and contrasted its performance to that of undefined inocula from activated sludge. Construction of the consortium was based on knowledge of the diversity of bacterial communities that naturally colonize MWF and determination of their catabolic abilities and tolerance to the chemical constituents. Chemical analysis of the inoculated MWF bioreactor revealed that, after 100 h at 28 degrees C, the defined inoculum reduced the pollution load by over 80% from an initial chemical oxygen demand of approximately 48 000 mg L(-)(1). The inocula performance was approximately 50% more effective than that of the undefined microbial community from the activated sludge. Furthermore, the performance of the constructed consortium was more reproducible than that of an undefined community, an essential feature for bioaugmentation treatment of industrial wastes.     

Gonadotropin-releasing hormone (GnRH): from fish to mammalian brains

1. This work deals with a family of neuropeptides, gonadotropin-releasing hormone (GnRH), that play a key role in the development and maintenance of reproductive function in vertebrates.2. Until now, a total of 16 GnRH structural variants have been isolated and characterized from vertebrate and protochordate nervous tissue. All vertebrate species already investigated have at least two GnRH forms coexisting in the central nervous system. However, it is now well accepted that three forms of GnRH in early and late evolved bony fishes are present.3. In these cases, cGnRH-II is expressed by midbrain neurons, a species-specific GnRH is present mainly in the preoptic area and the hypothalamus, and sGnRH is localized in the terminal nerve ganglion (TNG). In this context it is possible to think that three GnRH forms and three GnRH receptor (GnRH-R) subtypes are expressed in the central nervous system of a given species.4. Then it is possible to propose three different GnRH lineages expressed by distinct brain areas in vertebrates: (1) the conserved cGnRH-II or mesencephalic lineage; or (2) the hypothalamic or releasing lineage whose primary structure has diverged by point mutations (mGnRH and its orthologous forms: hrGnRH, wfGnRH, cfGnRH, sbGnRH, and pjGnRH); and (3) the telencephalic sGnRH form. Also different GnRH nomenclatures are discussed.     

Selection of microbial consortia for treating metal-working fluids

The aim of this research was to determine the effectiveness of a strategy for constructing microbial consortia for treating chemically mixed industrial effluent, based on a more thorough understanding of communities within waste metal-working fluids (MWFs). Complementary phenotypic and genotypic methods revealed that the microbial communities in spent MWFs had low diversity and were very similar in species composition in samples originating from different locations and uses. Of 65 bacterial isolates studied, only 9 species were identified using fatty acid methyl ester (FAME) analysis. The results of genotypic analysis by denaturing gradient gel electrophoresis (DGGE) were congruent with observations made using FAME analysis. The metabolic potential of the isolates was assessed in terms of assimilation ability and tolerance of co-contaminants. The three isolates, selected (Clavibacter michiganensis, Methylobacterium mesophilicum, and Rhodococcus erythropolis) to form a consortium, were representative of three of the four most abundant populations and when combined could utilise'or tolerate all of the individual MWF components, including the biocide and the recalcitrant compound benzotriazole. Journal of Industrial Microbiology & Biotechnology (2002) 29, 20–27 doi:10.1038/sj.jim.7000271 Received 19 December 2001/ Accepted in revised form 02 May 2002     

Asymmetric binding of the 1- and 4-C=O groups of QA in Rhodobacter sphaeroides R26 reaction centres monitored by Fourier transform infra-red spectroscopy using site-specific isotopically labelled ubiquinone-10.

Using 1-, 2-, 3- and 4-13C site-specifically labelled ubiquinone-10, reconstituted at the QA site of Rhodobacter sphaeroides R26 reaction centres, the infra-red bands dominated by the 1- and 4-C = O vibration of QA are assigned in the QA(-)-QA difference spectra. The mode dominated by the 4-C = O vibration is drastically downshifted in the reaction centres as compared with its absorption frequency in free ubiquinone-10. In contrast, the mode dominated by the 1-C = O vibration absorbs at similar frequencies in the free and the bound forms. The frequency shift of the 4-C = O vibration is due to a large decrease in bond order and indicates a strong interaction with the protein microenvironment in the ground state. In the charge-separated state the mode dominated by the semiquinone 4-C = O vibration is characteristic of strong hydrogen bonding to the microenvironment, whereas the mode dominated by the 1-C = O vibration indicates a weaker interaction. The asymmetric binding of the 1- and 4-C = O groups to the protein might contribute to the factors governing different redox reactions of ubiquinone-10 at the QA site as compared with its reactions at the QB site.     

Sequence variations in small-subunit ribosomal RNAs of Hartmannella vermiformis and their phylogenetic implications

Evidence of associations between free-living amoebas and human disease has been increasing in recent years. Knowledge about phylogenetic relationships that may be important for the understanding of pathogenicity in the genera involved is very limited at present. Consequently, we have begun to study these relationships and report here on the phylogeny of Hartmannella vermiformis, a free-living amoeba that can harbor the etiologic agent of Legionnaires' disease. Our analysis is based on studies of small-subunit ribosomal RNA genes (srDNA). Nucleotide sequences were determined for nuclear srDNA from three strains of H. vermiformis isolated from the United Kingdom, Germany, and the United States. These sequences then were compared with a sequence previously obtained for a North American isolate by J. H. Gunderson and M. L. Sogin. The four genes are 1,840 bp long, with an average GC content of 49.6%. Sequence differences among the strains range are 0.38%-0.76%. Variation occurs at 19 positions and includes 2 single-base indels plus 14 monotypic and 3 ditypic single-base substitutions. Variation is limited to eight helix/loop structures according to a current model for srRNA secondary structure. Parsimony, distance, and bootstrap analyses used to examine phylogenetic relationships between the srDNA sequences of H. vermiformis and other eukaryotes indicated that Hartmannella sequences were most closely related to those of Acanthamoeba and the alga Cryptomonas. All ditypic sites were consistent with a separation between European and North American strains of Hartmannella, but results of other tests of this relationship were statistically inconclusive.      

Transfer of light-induced electron-spin polarization from the intermediary acceptor to the prereduced primary acceptor in the reaction center of photosynthetic bacteria

In reaction centers and chromatophores of photosynthetic bacteria strong light-induced emissive ESR signals have been found, not only after a flash, but also under continuous illumination. The signal, with g = 2.0048 and ΔH_pp = 7.6 G, is only present under reducing conditions in material in which the primary acceptor, ubiquinone, U and its associated high-spin ferrous ion are magnetically uncoupled. Its amplitude under continuous illumination is strongly dependent on light intensity and on microwave power.

The emissive signal is attributed to the prereduced primary acceptor, U⁻, which becomes polarized through transfer of spin polarization by a magnetic exchange interaction with the photoreduced, spin polarized intermediary acceptor, I⁻. A kinetic model is presented which explains the observed dependence of emissivity on light intensity and microwave power. Applying this analysis to the light saturation data, a value of the exchange rate between I⁻ and U⁻ of 4 · 10⁸ s⁻¹ is derived, corresponding to an exchange interaction of 3–5 G.     

Studies on the binding of FMN by apoflavodoxin from Peptostreptococcus elsdenii, pH and NaCl concentration dependence.

1. The pH and ionic strength dependence of the interaction of FMN with apoflavodoxin has been studied by fluorometry in the pH region 2-5, at 22 degrees C. 2. The rate constant of dissociation and the dissociation constant were experimentally determined; the rate constants of association were claculated at a given pH value. These constants depend on the ionic strength. The plots of these constants against the square root of the ionic strength are straight. 3. Our data have been interpreted in terms of the Br?nsted theory, which relates chemical reaction rates to ionic strength. The data indicate that the apoenzyme reaches its maximum net positive charge at pH 2.0-2.6. The calculated net charge in this pH region is between 11 and 12 and is in agreement with the theoretical value of 12 as deduced from the primary structure of the protein. The isoelectric point of the holoenzyme is about 4. 4. The rate constant of association extrapolated to zero ionic strength is 3.2-10(5)M-1-s-1 and is pH-independent. 5. The rate constant of dissociation and the dissociation constant extrapolated to zero ionic strength depend on the pH. The results are explained by assuming that there are two protein ionizations with a pK value of 3.4; these ionizing groups are possibly close to the FMN binding site.     

A Phase 2a randomized,single-center,double-blind,placebo-controlled study to evaluate the safety and preliminary efficacy of oral iOWH032 against cholera diarrhea in a controlled human infection model

Cholera remains a major cause of infectious diarrhea globally. Despite the increased availability of cholera vaccines, there is still an urgent need for other effective interventions to reduce morbidity and mortality. Furthermore, increased prevalence of antibiotic-resistant Vibrio cholerae threatens the use of many drugs commonly used to treat cholera. We developed iOWH032, a synthetic small molecule inhibitor of the cystic fibrosis transmembrane conductance regulator chloride channel, as an antisecretory, host-directed therapeutic for cholera. In the study reported here, we tested iOWH032 in a Phase 2a cholera controlled human infection model. Forty-seven subjects were experimentally infected with V. cholerae El Tor Inaba strain N16961 in an inpatient setting and randomized to receive 500 mg iOWH032 or placebo by mouth every 8 hours for 3 days to determine the safety and efficacy of the compound as a potential treatment for cholera. We found that iOWH032 was generally safe and achieved a mean (± standard deviation) plasma level of 4,270 ng/mL (±2,170) after 3 days of oral dosing. However, the median (95% confidence interval) diarrheal stool output rate for the iOWH032 group was 25.4 mL/hour (8.9, 58.3), compared to 32.6 mL/hour (15.8, 48.2) for the placebo group, a reduction of 23%, which was not statistically significant. There was also no significant decrease in diarrhea severity and number or frequency of stools associated with iOWH032 treatment. We conclude that iOWH032 does not merit future development for treatment of cholera and offer lessons learned for others developing antisecretory therapeutic candidates that seek to demonstrate proof of principle in a cholera controlled human infection model study.Trial registration: This study is registered with ClinicalTrials.gov as {"type":"clinical-trial","attrs":{"text":"NCT04150250","term_id":"NCT04150250"}}NCT04150250.