A multilocus sequence typing (MLST) approach to diminish the problems that are associated with DNA barcoding: A reply to Stahlhut et al. (2012)

In a recent Perspective, Stahlhut et al. (2012) argued that potential Wolbachia-induced effects on inheritance patterns of mitochondrial DNA do not significantly affect DNA barcoding efforts. Since this hypothesis can be readily tested, we suggest to do so by including multiple, nuclear markers in DNA barcoding studies.     

Structural basis for lipoxygenase specificity. Conversion of the human leukocyte 5-lipoxygenase to a 15-lipoxygenating enzyme species by site-directed mutagenesis

Mammalian lipoxygenases constitute a heterogeneous family of lipid-peroxidizing enzymes, and the various isoforms are categorized with respect to their positional specificity of arachidonic acid oxygenation into 5-, 8-, 12-, and 15-lipoxygenases. Structural modeling suggested that the substrate binding pocket of the human 5-lipoxygenase is 20% bigger than that of the reticulocyte-type 15-lipoxygenase; thus, reduction of the active-site volume was suggested to convert a 5-lipoxygenase to a 15-lipoxygenating enzyme species. To test this "space-based" hypothesis of the positional specificity, the volume of the 5-lipoxygenase substrate binding pocket was reduced by introducing space-filling amino acids at critical positions, which have previously been identified as sequence determinants for the positional specificity of other lipoxygenase isoforms. We found that single point mutants of the recombinant human 5-lipoxygenase exhibited a similar specificity as the wild-type enzyme but double, triple, and quadruple mutations led to a gradual alteration of the positional specificity from 5S- via 8S- toward 15S-lipoxygenation. The quadruple mutant F359W/A424I/N425M/A603I exhibited a major 15S-lipoxygenase activity (85-95%), with (8S,5Z,9E,11Z,14Z)-8-hydroperoxyeicosa-5,9 ,11, 14-tetraenoic acid being a minor side product. These data indicate the principle possibility of interconverting 5- and 15-lipoxygenases by site-directed mutagenesis and appear to support the space-based hypothesis of positional specificity.     

The insulin-like effect of growth hormone on insulin-like growth factor II receptors is opposed by cyclic AMP. Evidence for a common post-receptor pathway for growth hormone and insulin action.

The counter-regulatory effects of beta-adrenergic stimulation and cyclic AMP on the insulin-like action of growth hormone (GH) on the subcellular distribution of insulin-like growth factor II (IGF-II) receptors were studied in fat cells from hypophysectomized (Hx) and sham-operated rats. For comparison, the effect of insulin on this process was also studied. Basal IGF-II binding was increased by approx. 2-fold in cells from Hx as compared with sham-operated animals. The stimulatory effect of insulin was decreased in Hx cells, mainly due to a basal redistribution but also to a reduced total number of receptors. GH exerted an acute insulin-like effect in cells from Hx rats and stimulated the translocation of IGF-II receptors from an intracellular pool to the plasma membrane. beta-Adrenergic stimulation with isoprenaline or addition of the non-metabolizable cyclic AMP-analogue N6-monobutyryl cyclic AMP induced a cellular resistance to both GH and insulin and also reduced the responsiveness to these hormones. Adenosine exerted a modulatory effect on both hormones. Binding of 125I-labelled GH to its receptors was not significantly changed by any of these factors. It is concluded that: (1) beta-adrenergic stimulation and cyclic AMP induce a cellular GH resistance at a level distal to the GH-binding site, and (2) the insulin-like effect of GH shares a common pathway with insulin which occurs at the post-binding level.     

Assembly and crystallization of the complex between the human T cell coreceptor CD8alpha homodimer and HLA-A2.

A strategy for overexpression in Escherichia coli of the extracellular immunoglobulin domain of human CD8alpha was devised using codon usage alterations in the 5' region of the gene, designed so as to prevent the formation of secondary structures in the mRNA. A fragment of CD8alpha, comprising residues 1-120 of the mature protein, excluding the signal peptide and the membrane-proximal stalk region, was recovered from bacterial inclusion bodies and refolded to produce a single species of homodimeric, soluble receptor. HLA-A2 heavy chain, beta2-microglobulin and a synthetic peptide antigen corresponding to the pol epitope from HIV-1 were also expressed in E. coli, refolded and purified. CD8alpha/HLA-A2 complexes were formed in solution and by co-crystallization with a stoichiometry of one CD8alpha alpha dimer to one HLA-A2-peptide unit.     

Exon Inclusion Modulates Conformational Plasticity and Autoinhibition of the Intersectin 1 SH3A Domain

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Bioprospecting the African Renaissance: The new value of <Emphasis Type="Italic">muthi</Emphasis> in South Africa

This article gives an overview of anthropological research on bioprospecting in general and of available literature related to bioprospecting particularly in South Africa. It points out how new insights on value regimes concerning plant-based medicines may be gained through further research and is meant to contribute to a critical discussion about the ethics of Access and Benefit Sharing (ABS). In South Africa, traditional healers, plant gatherers, petty traders, researchers and private investors are assembled around the issues of standardization and commercialization of knowledge about plants. This coincides with a nation-building project which promotes the revitalization of local knowledge within the so called African Renaissance. A social science analysis of the transformation of so called Traditional Medicine (TM) may shed light onto this renaissance by tracing social arenas in which different regimes of value are brought into conflict. When medicinal plants turn into assets in a national and global economy, they seem to be manipulated and transformed in relation to their capacity to promote health, their market value, and their potential to construct new ethics of development. In this context, the translation of socially and culturally situated local knowledge about muthi into global pharmaceuticals creates new forms of agency as well as new power differentials between the different actors involved.     

Untersuchungen zur lichtinduzierten Hemmung der Ascosporenbildung bei Saccharomyces cerevisiae

Zusammenfassung Die Ascosporenbildung wird durch sichtbares Licht in zweifacher Weise beeinflußt, a) durch Blockierung der Ascusbildung in einem Teil der Zellen (= 1. Lichteffekt) und b) durch Verzögerung des Sporulationsbeginns (=2. Lichteffekt). Der wirksame Spektralbereich im sichtbaren Bereich des Spektrums liegt bei Wellenlängen um 400–500 nm, während Rotlicht keinen Einfluß ausübt. Der 1. Lichteffekt (Hemmung der Sporulation) ist anscheinend unspezifischer Natur, betrifft z. B. nicht spezifisch die Meiose, da Licht während der vormeiotischen Periode der Sporulationskultur gleich stark wirkt wie Licht, das erst während und nach der Meiose eingestrahlt wird. Bei Belichtung beider Abschnitte wird etwa die doppelte Wirkung erzielt. Das Ausmaß der Hemmung ist unabhängig von der Dauer der Vorkultur. Dagegen ist der 2. Lichteffekt (Verzögerung des Sporulations-beginns) stärker bei Zellen aus der 1. Vermehrungsphase der Vorkultur als bei solchen aus der zweiten und betrifft offenbar Prozesse, die mit der Assimilation, nicht aber mit der Oxidation von C2-Körpern wie Äthanol (Vorkultur) bzw. Acetat (Sporulationskultur) zusammenhängen. Dies wird aus folgenden Ergebnissen geschlossen: nur geringfügige Hemmung der O₂-Aufnahme, Möglichkeit der Unterdrückung der 2. Vermehrungsphase durch Belichtung der Vorkultur und lichtbedingte Hemmung des in der Anfangsphase der Sporulationskultur erfolgenden Wachstums. Die Hemmung der Äthanol-bzw. Acetatassimilation läßt sich jedoch nicht oder nicht allein aus einer nur vergleichsweise geringen lichtinduzierten Aktivitätserniedrigung der Glyoxylatcyclusenzyme erklären.

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Studies on the light-induced inhibition of ascospore formation in Saccharomyces cerevisiae

Summary Visible light influences sporulation in two different ways: a) by completely blocking ascospore formation in a varying percentage of the cells dependent on the intensity and duration of illumination, and b) by delaying the onset of sporulation. Blue light (400–500 nm) is found to be responsible for both these effects while red light (600–700 nm) is ineffective. The first effect of light i.e. the inhibition of ascospore formation seems to be nonspecific. There is e.g. no specific effect on meiosis, since the inhibition of sporulation is the same whether the illumination is given during the premeiotic period or during the meiotic and postmeiotic period. The inhibition is twice as high when the cells have been illuminated during both periods. The extent of inhibition is independent of the length of the preculture. On the other hand, the second effect of light (delay of sporulation onset) is stronger with cells from the first phase than with those from the second phase of exponential growth. This effect seems to be concerned with processes of assimilation of C2-compounds such as ethanol (preculture) or acetate (sporulation culture), respectively, but it has nothing or almost nothing to do with the oxidation of these compounds. This is concluded from the following results: only little inhibition of O₂-consumption, light-induced suppression of the second growth phase of the preculture and inhibition of the growth which normally occurs during the first hours in the sporulation medium. The inhibition of ethanol or acetate assimilation is only partly explained by the comparably small light-induced decline of the activity of glyoxylate cycle enzymes.