Billingen (Lower Arenig/Lower Ordovician) acritarchs from the East European Platform and their palaeobiogeographic significance

Billingen (Lower Arenig/Lower Ordovician) sediments of the St. Petersburg region, northwest Russia and the Leba area, northern Poland of the East European Craton yield acritarch assemblages, which are largely homogenous though displaying minor compositional differences that probably reflect a gradient from inner to outer shelf environments. Comparison with coeval acritarch microflora from the Yangtze Platform, South China, shows an overall similarity between Baltoscandian and South Chinese phytoplankton. The widespread uniformity in the fossil microphytoplankton may be related to the extensive global 'evae' sea-level transgression, which characterized the Billingen time. This suggests that during the Tremadoc through early Arenig times, acritarch assemblages displayed essentially an undifferentiated cold-water and oceanic character along the whole margin of Perigondwana in the South, as well as on the South Chinese and Baltic platforms, at middle latitudes (Mediterranean oceanic Realm). Despite this overall similarity, however, some typical taxa of the high-latitude Mediterranean Province (Arbusculidium, Coryphidium and Striatotheca) occur in South China, but are absent in Baltica. This discrepancy is explained as caused by differences in climatic and physiographic conditions that prevailed at the two palaeocontinents at this time. The inferred pattern of oceanic circulation during the Lower Ordovician is consistent with the palynological evidence of a prevailing warmer climate in Baltica than in South China, although the two palaeocontinents occupied the same palaeolatitudinal position.     

Human catecholamine sulfotransferase (SULT1A3) pharmacogenetics: functional genetic polymorphism

Sulfotransferase (SULT) 1A3 catalyzes the sulfate conjugation of catecholamines and structurally related drugs. As a step toward studies of the possible contribution of inherited variation in SULT1A3 to the pathophysiology of human disease and/or variation in response to drugs related to catecholamines, we have resequenced all seven coding exons, three upstream non-coding exons, exon-intron splice junctions and the 5'-flanking region of SULT1A3 using DNA samples from 60 African-American (AA) and 60 Caucasian-American (CA) subjects. Eight single nucleotide polymorphisms (SNPs) were observed in AA and five in CA subjects, including one non-synonymous cSNP (Lys234Asn) that was observed only in AA subjects with an allele frequency of 4.2%. This change in amino acid sequence resulted in only 28 +/- 4.5% (mean +/- SEM) of the enzyme activity of the wild-type (WT) sequence after transient expression in COS-1 cells, with a parallel decrease (54 +/- 2.2% of WT) in level of SULT1A3 immunoreactive protein. Substrate kinetic studies failed to show significant differences in apparent Km values of the two allozymes for either dopamine (10.5 versus 10.2 micro m for WT and variant, respectively) or the cosubstrate 3'-phosphoadenosine 5'-phosphosulfate (0.114 versus 0.122 micro m, respectively). The decrease in level of immunoreactive protein in response to this single change in amino acid sequence was due, at least in part, to accelerated SULT1A3 degradation through a proteasome-mediated process. These observations raise the possibility of ethnic-specific inherited alterations in catecholamine sulfation in humans.     

Cyrtocrinids (Echinodermata,Crinoidea) from Upper Jurassic Štramberk‐type limestones in southern Poland

Abstract: A systematic account of highly diverse cyrtocrinid faunules from Upper Jurassic strata of ?tramberk type (Oxfordian–Tithonian) in southern Poland (Polish Carpathians) is presented. Fourteen taxa (Phyllocrinus malbosianus, Ph. stellaris, Ph. sp., Psalidocrinus armatus, Sclerocrinus compressus, S. polonicus sp. nov., Hemicrinus aff. kabanovi, Ancepsicrinus parvus gen. et sp. nov., Tetracrinus baumilleri sp. nov., Eugeniacrinites alexandrowiczi, E. cf. moravicus, E. sp., Eudesicrinus gluchowskii sp. nov. and Hemibrachiocrinus tithonicus sp. nov. are described and illustrated. Representatives of the genus Eudesicrinus, previously recorded only from the Lower Jurassic, are here shown to extend into the uppermost Jurassic. Other cyrtocrinids considered are common in Jurassic/Cretaceous strata across Europe. In the present faunules, isocrinid (Isocrinida), comatulid (Comatulida) and roveacrinid (Roveacrinida sensu Rasmussen, inclusive of Saccocoma) crinoids are associated.     

A glucose kinase from Mycobacterium smegmatis

Carbon metabolism and regulation is poorly understood in mycobacteria, a genus that includes some major pathogenic species like Mycobacterium tuberculosis and Mycobacterium leprae. Here, we report the identification of a glucose kinase from Mycobacterium smegmatis. This enzyme serves in glucose metabolism and global carbon catabolite repression in the related actinomycete Streptomyces coelicolor. The gene, msmeg1356 (glkA), was found by means of in silico screening. It was shown that it occurs in the same genetic context in all so far sequenced mycobacterial species, where it is located in a putative tricistronic operon together with a glycosyl hydrolase and a putative malonyl-CoA transacylase. Heterologous expression of glkA in an Escherichia coli glucose kinase mutant led to the restoration of glucose growth, which provided in vivo evidence for glucose kinase function. GlkA(Msm) was subsequently overproduced in order to study its enzymatic features. We found that it can form a dimer and that it efficiently phosphorylates glucose at the expense of ATP. The affinity constant for glucose was with 9 mM about eight times higher and the velocity was about tenfold slower when compared to the parallel measured glucose kinase of S. coelicolor. Both enzymes showed similar substrate specificity, which consists in an ATP-dependent phosphorylation of glucose and no, or very inefficient, phosphorylation of the glucose analogues 2-deoxyglucose and methyl alpha-glucoside. Hence, our data provide a basis for studying the role of mycobacterial glucose kinase in vivo to unravel possible catalytic and regulatory functions.     

A new piece of an old jigsaw: glucose kinase is activated posttranslationally in a glucose transport-dependent manner in streptomyces coelicolor A3(2)

Members of the soil-dwelling prokaryotic genus Streptomyces are indispensable for the recycling of complex polysaccharides, and produce a wide range of natural products. Nutrient limitation is likely to be a major signal for the onset of their development, resulting in spore formation by specialized aerial hyphae. Streptomycetes grow on numerous carbon sources, which they utilize in a preferential manner. The main signaling pathway underlying this phenomenon is carbon catabolite repression, which in streptomycetes is totally dependent on the glycolytic enzyme glucose kinase (Glk). How Glk exerts this fascinating dual role (metabolic and regulatory) is still largely a mystery. We show here that while Glk is made constitutively throughout the growth of Streptomyces coelicolor A3(2), its catalytic activity is modulated in a carbon source-dependent manner: while cultures growing exponentially on glucose exhibit high Glk activity, mannitol- grown cultures show negligible activity. Glk activity was directly proportional to the amount of two Glk isoforms observed by Western blot analysis. The activity profile of GlcP, the major glucose permease, correlated very well with that of Glk. Our data are consistent with a direct interaction between Glk and GlcP, suggesting that a Glk-GlcP permease complex is required for efficient glucose transport by metabolic trapping. This is supported by the strongly reduced accumulation of glucose in glucose kinase mutants. A model to explain our data is presented.