Occurrence of Prorocentrum lima,a DSP toxin-producing species from the Atlantic coast of Canada

A species of Prorocentrum (Dinophyta, Prorocentrales), isolated from a phytoplankton net sample from the Atlantic coast of Nova Scotia, has been brought into unialgal culture. The sample was collected at an aquaculture site immediately following an incident of diarrhetic shellfish poisoning (DSP) due to the consumption of contaminated mussels. This clonal isolate has been identified as P. lima, based on its morphological characteristics. Analysis of the culture extract, using high performance liquid chromatography (HPLC) with fluorescence detection, indicated the presence of the DSP toxins, okadaic acid (OA) and dinophysistoxin-1 (DTX-1).     

Interleukin-1 inhibits PGE2 binding to macrophage-like P388D1 cells by a cyclic AMP-independent process

The interaction between interleukin IL-1α and PGE₂ on P388D₂ on cells has been investigated. Preincubation of murine macrophage-like cells, P388D₁, with IL-1α (0–73 pM) reduced the binding of PGE₂ to these cells in a concentration-dependent manner. Scatchard analysis showed that IL-1α decreased the PGE₂ binding by lowering both the high and low affinity receptor binding capacities (from 0.31 ± 0.02 to 0.12 ± 0.01 fmol/10⁶ cells for the high affinity receptor binding sites and from 2.41 ± 0.12 to 1.51 ± 0.21 fmol/10⁶ cells for the low affinity receptor binding sites). However, the dissociation constants of the receptor of the IL-1α-treated cells remained unchanged. Inhibition of PGE₂ binding IL-1α did not involve changes in either protein phosphorylation or intracellular cyclic AMP levels. Our data clearly show that IL-1α inhibits the binding of PGE₂ to monocytes/macrophages and may thereby counter the immunosuppressive actions of PGE₂.     

A semiempirical study of the prototropic tautomerism of hypoxanthine

The total and relative energies, bond order matrices and localized MOs for the eight possible tautomers of hypoxanthine (HYP) have been calculated, with full geometry optimization, using both AM1 and MNDO methods. The AM1 relative energies show that HYP(9,1), HYP(7,1) and HYP (9,10) are the predominant species at room temperature, the two former being in larger concentration that the latter. The calculated IR spectra for these species agree well with the reported spectrum in an isolated matrix, which has been interpreted in terms of the presence of these three tautomeric forms. The MNDO method does not predict the right order, and the more stable tautomer would be HYP(9,10). The calculated structure for the HYP(9,1) species shows that the molecule is essentially planar. The bond distances compare well with those of hypoxanthine hydrochloride and guanine and also correlate well with the calculated bond orders. The proton affinities for the three more stable tautomers have also been calculated. For HYP(9,1) the prefered site of protonation is N7, whereas for HYP(7,1) the protonation occurs rather at N9. These results agree well with¹⁵N and¹³C NMR studies in DMSO.     

Catalytically competent human and bovine zeta-thrombin and chimeras generated from unfolded polypeptide chains.

Human and bovine alpha-thrombin cleaved at the B-chain by chymotrypsin generates catalytically competent zeta-thrombins, which are comprised of two noncovalently linked fragments: a 36-(human) or 49-(bovine) residue A-chain linked by a disulfide to B-chain residues B1-148 (zeta 1-thrombin) and B-chain residues B149-259 (zeta 2-thrombin). Human and bovine D-Phe-Pro-Arg-CH2-zeta- and PhMeSO2-zeta-thrombins were prepared by reaction of the active-site histidine (H-B43) and serine (S-B205) with PPACK and PMSF, respectively. Unfolding and dissociation of the noncovalently linked polypeptide chains of either human or bovine D-Phe-Pro-Arg-CH2-zeta- and PhMeSO2-zeta-thrombins in 4.5 M guanidine-HCl and refolding upon 30-fold dilution in 50 mM sodium phosphate buffer pH 6.5, 750 mM NaCl, 0.1% PEG resulted in biphasic generation of catalytic activity. The slow phase was eliminated in the presence of the competitive inhibitor benzamidine-HCl. Unfolding and refolding mixtures of the appropriate inactive precursors generated the active chimeric thrombins bovine zeta 1-thrombin:human zeta 2-thrombin and human zeta 1-thrombin:bovine zeta 2-thrombin. Human zeta 1-thrombin and zeta 2-thrombin were isolated, and, upon recombining, the isolated fragments refolded to generate catalytically competent zeta-thrombin with an active-site content, specific activity toward Chromozym-TH, and a specificity constant (kcat/Km) for FPA release from fibrinogen that were all within 60% of those of native alpha-thrombin.(ABSTRACT TRUNCATED AT 250 WORDS)     

1H NMR investigation of reduced copper-cobalt superoxide dismutase

Human copper-cobalt superoxide dismutase in the reduced form has been investigated through ¹H NMR techniques. The aim is to monitor the structural properties of this derivative and to compare them with those of reduced and oxidized native superoxide dismutases. The observed signals of the cobalt ligands have been assigned as well as the signals of the histidines bound to copper(I). The latter signals experience little pseudocontact shifts which allow a rough orientation of the magnetic susceptibility tensor in the molecular frame. The connectivities indicate that, although the histidine bridge is broken in the reduced form, the interproton distances between ligands of both ions are essentially the same.Abbreviations WEFT water eliminated Fourier transform - NOE nuclear Overhauser effect - NOESY NOE spectroscopy - COSY correlation spectroscopy - TOCSY total correlation spectroscopy - SOD superoxide dismutase - E₂Co(II)SOD SOD with empty copper site (E=empty) and with cobalt(II) in the Zinc(II) site Offprint requests to: I. Bertini     

Changes of carp myosin subfragment-1 induced by temperature acclimation

Summary Heavy meromyosin subfragment-1 (S1) was prepared by -chymotrypsin from myosin of carp acclimated to either 10°C or 30°C for a minimum of 5 weeks. The objective of these studies was to document thermally-induced changes in the myosin molecule and to extend previous observations. Ca²⁺- and K⁺ (EDTA)-ATPase activities of cold-acclimated carp S1 were 1.1 and 0.8 mol P_i·min^-1·mg^-1, respectively, and these values did not differ significantly from those of warm-acclimated carp. The inactivation rate constant (K_D) of S1 from cold-acclimated carp was 32.1x10^-4· s^-1, compared to 13.2x10^-4·s^-1 for warm-acclimated carp. The maximum initial velocity of acto-S1 Mg²⁺-ATPase activity at pH 7.0 in 0.05 M KCl was 9.3 s^-1 with cold-acclimated carp, about 3.7 times higher than that for warm-acclimated carp. However, no significant difference was observed in the apparent affinity of S1 to actin. Peptides maps of the heavy chain of S1 were different and suggested distinct isoforms for the myosins from warm- and cold-acclimated muscle.Abbreviations ATPase adenosine 5-triphosphatase - DTNB 5,5-dithiobis (2-nitrobenzoic acid) - DTT dithiothreitol - EDTA ethylenediaminetetraacetic acid - EGTA ethyleneglycol bis (-aminoethylether)-N,N,N,N-tetraacetic acid - K _D inactivation rate constant - K _m apparent dissociation constant - P _i inorganic -phosphate - PMSF phenylmethane-sulfonyl fluoride - S ₁ heavy meromyosin subfragment-1 - SDS sodium dodecyl sulfate - SDS-PAGE SDS-polyacrylamide gel electrophoresis - TPCK N-tosyl-l-phenylalanyl chloromethyl ketone - V _max maximum initial velocity     

Different oligosaccharides accumulate in the brain and urine of a cat with α-mannosidosis: structure determination of five brain-derived and seventeen urinary oligosaccharides

Five brain-derived and 17 urinary oligomannose-type oligosaccharides were isolated by ion-exchange chromatography on Mono Q or Dowex, followed by HPLC on Lichrosorb-NH₂ from a Persian cat suffering from -mannosidosis. The structures ofthe carbohydrate chains were determined by 500- or 600-MHz¹H-NMR spectroscopy. Different oligosaccharide patterns were found in brain and urine. 99% of the urinary oligosaccharides possess an (1-6)-linked mannose residue attached to -mannose, whereas only 5% of the brain-derived oligosaccharides contain such a residue. Furthermore, of the urinary carbohydrate chains 71% end with Man1-4GlcNAc1-4GlcNAc and 29% end with Man1-4GlcNAc, whereas the corresponding amounts are 23% and 77%, respectively, for the brain-derived oligosaccharides.Abbreviations MLEV-17 composite pulse devised by M. Levitt - HOHAHA homonuclear Hartman-Hahn spectroscopy - TPPI time-proportional phase incrementation - 2D two dimensional - GlcNAc N-acetylglucosamine - Man mannose - Fuc fucose     

Structures of the α(1-3)-galactose-containing asparagine-linked glycans of a Lewis lung carcinoma cell subline resistant toAleuria aurantia agglutinin: elucidation by1H-NMR spectroscopy

Four bi-antennary glycan fractions of theN-acetyllactosamine-type, derived from a Lewis lung carcinoma (LL₂) cell subline resistant to theAleuria aurantia agglutinin were studied by 400 MHz¹H-NMR spectroscopy. By this method, their antennae were found to be terminated either by (2-3 or 6)-linkedN-acetylneuraminic acid or (1-3)-linked galactose residues. The primary structure of glycans of these four glycopeptide or derived oligosaccharide-alditols has been determined in full detail.Abbreviations NAc N-acetyl group - NGc N-glycolyl group - GlcNAc N-acetylglucosamine - NeuAc N-acetylneuraminic acid - NeuGc N-glycolylneuraminic acid - Man mannose - Gal galactose - Fuc fucose - Con A concanavalin A - LCA Lens culinaris agglutinin - AAA Aleuria aurantia agglutinin - WGA Wheat germ agglutinin - RCA II Ricinus communis agglutinin II - PBS phosphate buffered saline, 0.01m Na₂HPO₄/0.14m NaCl, pH 7.2 - HPLC high performance liquid chromatography - EMEM Eagle's Minimal Essential Medium - Lec^R lectin resistant - MG -methylglycoside     

The electron transport system of Alcaligenes eutrophus H16

In a previous work (Kömen et al. 1991) it has been concluded that membrane fragments isolated from autotrophically grown Alcaligenes eutrophus H16 contain several iron-sulphur centres along with haems of a-, b-, c-, and d-type. These redox components have been proposed to be part of a branched respiratory chain leading to multiple membrane bound oxidases. Here, some of the respiratory activities catalyzed by membrane fragments from wild type cells of A. eutrophus (H16) and, for comparison, Paracoccus denitrificans, have been investigated through the use of electron transport inhibitors. Cyanide (CN^-) titration curves indicated that in A. eutrophus H16 oxidation of succinate and H₂ preferentially proceeds via the cytochrome c oxidase(s) branch (I ₅₀=2 · 10^-5 M) whereas the NADH dependent respiration started being inhibited at higher CN^- concentrations (I ₅₀=5 · 10^-4 M). In membranes isolated from both, cells harvested at late growth-phase (OD 12) and from a mutant deficient in cytochrome c oxidase activity (A. eutrophus RK1), respiration was insensitive to low CN^- concentrations (< 10^-4 M), and it was sustained by the high catalytic activities of two quinol oxidases. These alternative oxidases of b- (formally o-) and d-type showed different sensitivities to KCN (I ₅₀=10^-3 M and 10^-2 M, respectively). Interestingly, the cytochrome c oxidase(s) dependent respiration of H16 membranes was insensitive to antimycin A but largely inhibited by myxothiazol (10^-6 M). This, and previous work (Kömen et al. 1991), suggest that although the respiratory chain of A. eutrophus is endowed with a putative bc ₁ complex, its biochemical nature and role in respiration of this organism are apparently different from those of P. denitrificans. The peculiarity of the respiratory chain of A. eutrophus is confirmed by the rotenone insensitivity of the NADH oxidation in both protoplasts and membrane fragments from wild type and soluble hydrogenase deficient cells (HF14 and HF160). A tentative model of the respiratory chain of autotrophically grown A. eutrophus is presented.     

Structure and expression of the Chlorobium vibrioforme hemA gene

The green sulfur bacterium, Chlorobium vibrioforme, synthesizes the tetrapyrrole precursor, -aminolevulinic acid (ALA), from glutamate via the RNA-dependent five-carbon pathway. A 1.9-kb clone of genomic DNA from C. vibrioforme that is capable of transforming a glutamyl-tRNA reductase-deficient, ALA-dependent, hemA mutant of Escherichia coli to prototrophy was sequenced. The transforming C. vibrioforme DNA has significant sequence similarity to the E. coli, Salmonella typhimurium, and Bacillus subtilis hemA genes and contains a 1245 base open reading frame that encodes a 415 amino acid polypeptide with a calculated molecular weight of 46174. This polypeptide has over 28% amino acid identity with the polypeptides deduced from the nucleic acid sequences of the E. coli, S. typhimurium, and B. subtilis hemA genes. No sequence similarity was detected, at either the nucleic acid or the peptide level, with the Rhodobacter capsulatus or Bradyrhizobium japonicum hemA genes, which encode ALA synthase, or with the S. typhimurium hemL gene, which encodes glutamate-1-semialdehyde aminotransferase. These results establish that hemA encodes glutamyl-tRNA reductase in species that use the five-carbon ALA biosynthetic pathway. A second region of the cloned DNA, located downstream from the hemA gene, has significant sequence similarity to the E. coli and B. subtilis hemC genes. This region contains a potential open reading frame that encodes a polypeptide that has high sequence identity to the deduced E. coli and B. subtilis HemC peptides. hemC encodes the tetrapyrrole biosynthetic enzyme, porphobilinogen deaminase, in these species. Preliminary evidence was obtained for the existence of a 3.0-kb polycistronic meassge that includes the hemA sequence, in exponentially growing C. vibrioforme cells. Results of condon usage analysis for the C. vibrioforme hemA gene indicate that green sulfur bacteria are more closely related to purple nonsulfur bacteria than to enteric bacteria. Sequences corresponding to a polyadenylation signal and a poly(A) attachment site were found immediately downstream from the 3 end of the hemA open reading frame.