Genetic diversity,evolutionary history and implications for conservation of the lion (Panthera leo) in West and Central Africa

Aim In recent decades there has been a marked decline in the numbers of African lions (Panthera leo), especially in West Africa where the species is regionally endangered. Based on the climatological history of western Africa, we hypothesize that West and Central African lions have a unique evolutionary history, which is reflected by their genetic makeup. Location Sub‐Saharan Africa and India, with special focus on West and Central Africa. Method In this study 126 samples, throughout the lion’s complete geographic range, were subjected to phylogenetic analyses. DNA sequences of a mitochondrial region, containing cytochrome b, tRNAPro, tRNAThr and the left part of the control region, were analysed. Results Bayesian, maximum likelihood and maximum parsimony analyses consistently showed a distinction between lions from West and Central Africa and lions from southern and East Africa. West and Central African lions are more closely related to Asiatic lions than to the southern and East African lions. This can be explained by a Pleistocene extinction and subsequent recolonization of West Africa from refugia in the Middle East. This is further supported by the fact that the West and Central African clade shows relatively little genetic diversity and is therefore thought to be an evolutionarily young clade. Main conclusions The taxonomic division between an African and an Asian subspecies does not fully reflect the overall genetic diversity within lions. In order to conserve genetic diversity within the species, genetically distinct lineages should be prioritized. Understanding the geographic pattern of genetic diversity is key to developing conservation strategies, both for in situ management and for breeding of captive stocks.     

Sulfolobus solfataricus translation initiation factor 1 stimulates translation initiation complex formation

The eukaryotic translation initiation factor 1 binds to the ribosome during translation initiation. It is instrumental for initiator-tRNA and mRNA binding, and has a function in selection of the authentic start codon. Here, we show that the archaeal homolog aIF1 has analogous functions. The aIF1 protein of the archaeon Sulfolobus solfataricus is bound to the small ribosomal subunit during translation initiation and accelerates binding of initiator-tRNA and mRNA to the ribosome. Accordingly, aIF1 stimulated translation of an mRNA in a S. solfataricus in vitro translation system. Moreover, this study suggested that the C terminus of the factor is of relevance for its function.     

Influence of substrate supply on the production of sophorose lipids by Candida bombicola ATCC 22214

Summary Candida (Torulopsis) bombicola ATCC 22214 produces 180 g/l sophorose lipids using glucose and oleic acid (technical grade) as combined substrates in an extended fed-batch cultivation. Excess of oleic acid generated a paste-like product. However, only when oleic acid was not detectable during the whole run of cultivation, a microcrystalline product precipitated. The unsaturated C-18 fatty acids of the technical grade oleic acid were transferred unchanged into the sophorose lipid.     

Congruence between mitochondrial genes and color morphs in a coral reef fish: population variability in the Indo-Pacific damselfish Chrysiptera rex (Snyder, 1909)

The Pomacentrid fish Chrysiptera rex (Snyder 1909) is a small conspicuous member of Indo-Pacific coral reefs. Despite having planktonic larvae, which would seem to facilitate genetic and morphological homogeneity, it possesses three distinct color variations, which are geographically restricted. To investigate the presence of possible incipient speciation, samples were taken from three geographically distinct areas including the South China Sea, the Philippines and Indonesia. Phylogenetic analysis of these morphotypes resulted in congruence between color and genetic data sets, with separation by color type. Each of the color variants possessed a unique genetic signal at two mitochondrial loci, but the color variants were invariant across a nuclear gene. This study highlights the importance of range wide sampling when characterizing a species and argues that multiple lines of evidence should be used when evaluating the taxonomic and conservation status of coral reef organisms.     

Depolarization of the membrane potential by hyaluronan

The membrane potential is mainly maintained by the K⁺ concentration gradient across the cell membrane between the cytosol and the extracellular matrix. Here, we show that extracellular addition of high‐molecular weight hyaluronan depolarized the membrane potential of human fibroblasts, human embryonic kidney cells (HEK), and central nervous system neurons in a concentration‐dependent manner, whereas digestion of cell surface hyaluronan by hyaluronidase caused hyperpolarization. This effect could not be achieved by other glycosaminoglycans or hyaluronan oligosaccharides, chondroitin sulfate, and heparin which did not affect the membrane potential. Mixtures of high‐molecular weight hyaluronan and bovine serum albumin had a larger depolarization effect than expected as the sum of both individual components. The different behavior of high‐molecular weight hyaluronan versus hyaluronan oligosaccharides and other glycosaminoglycans can be explained by a Donnan effect combined with a steric exclusion of other molecules from the water solvated chains of high‐molecular weight hyaluronan. Depolarization of the plasma membrane by hyaluronan represents an additional pathway of signal transduction to the classical CD44 signal transduction pathway, which links the extracellular matrix to intracellular metabolism. J. Cell. Biochem. 111: 858–864, 2010. © 2010 Wiley‐Liss, Inc.     

Regulation of cell volume by glycosaminoglycans

Cell volume is regulated by a delicate balance between ion distribution across the plasma membrane and the osmotic properties of intra‐ and extracellular components. Using a fluorescent calcein indicator, we analysed the effects of glycosaminoglycans on the cell volume of hyaluronan producing fibroblasts and hyaluronan deficient HEK cells over a time period of 30 h. Exogenous glycosaminoglycans induced cell blebbing after 2 min and swelling of fibroblasts to about 110% of untreated cell volume at low concentrations which decreased at higher concentrations. HEK cells did not show cell blebbing and responded by shrinking to 65% of untreated cell volume. Heparin induced swelling of both fibroblasts and HEK cells. Hyaluronidase treatment or inhibition of hyaluronan export led to cell shrinkage indicating that the hyaluronan coat maintained fibroblasts in a swollen state. These observations were explained by the combined action of the Donnan effect and molecular crowding. J. Cell. Biochem. 113: 340–348, 2012. © 2011 Wiley Periodicals, Inc.     

A Novel Pex14 Protein-interacting Site of Human Pex5 Is Critical for Matrix Protein Import into Peroxisomes

Protein import into peroxisomes relies on the import receptor Pex5, which recognizes proteins with a peroxisomal targeting signal 1 (PTS1) in the cytosol and directs them to a docking complex at the peroxisomal membrane. Receptor-cargo docking occurs at the membrane-associated protein Pex14. In human cells, this interaction is mediated by seven conserved diaromatic penta-peptide motifs (WXXX(F/Y) motifs) in the N-terminal half of Pex5 and the N-terminal domain of Pex14. A systematic screening of a Pex5 peptide library by ligand blot analysis revealed a novel Pex5-Pex14 interaction site of Pex5. The novel motif composes the sequence LVAEF with the evolutionarily conserved consensus sequence LVXEF. Replacement of the amino acid LVAEF sequence by alanines strongly affects matrix protein import into peroxisomes in vivo. The NMR structure of a complex of Pex5-(57–71) with the Pex14-N-terminal domain showed that the novel motif binds in a similar α-helical orientation as the WXXX(F/Y) motif but that the tryptophan pocket is now occupied by a leucine residue. Surface plasmon resonance analyses revealed 33 times faster dissociation rates for the LVXEF ligand when compared with a WXXX(F/Y) motif. Surprisingly, substitution of the novel motif with the higher affinity WXXX(F/Y) motif impairs protein import into peroxisomes. These data indicate that the distinct kinetic properties of the novel Pex14-binding site in Pex5 are important for processing of the peroxisomal targeting signal 1 receptor at the peroxisomal membrane. The novel Pex14-binding site may represent the initial tethering site of Pex5 from which the cargo-loaded receptor is further processed in a sequential manner.     

Investigations on small molecule inhibitors targeting the histone H3K4 tri-methyllysine binding PHD-finger of JmjC histone demethylases

Plant homeodomain (PHD) containing proteins are important epigenetic regulators and are of interest as potential drug targets. Inspired by the amiodarone derivatives reported to inhibit the PHD finger 3 of KDM5A (KDM5A(PHD3)), a set of compounds were synthesised. Amiodarone and its derivatives were observed to weakly disrupt the interactions of a histone H3K4me3 peptide with KDM5A(PHD3). Selected amiodarone derivatives inhibited catalysis of KDM5A, but in a PHD-finger independent manner. Amiodarone derivatives also bind to H3K4me3-binding PHD-fingers from the KDM7 subfamily. Further work is required to develop potent and selective PHD finger inhibitors.     

Urease from Staphylococcus saprophyticus: purification,characterization and comparison to Staphylococcus xylosus urease

Urease from Staphylococcus saprophyticus was purified more than 800-fold by liquid chromatography reaching homogeneity, as shown by isoelectric focussing, at a maximum specific activity of 1979 U/mg. The molecular weight of the native enzyme was 420000; it consisted of subunits with molecular weights of 72400 (), 20400 (), and 13900 () in an estimated ()₄ stoichiometry. In native gradient polyacrylamide gel electrophoresis urease exhibited a multiple activity band pattern with molecular weights ranging from 420000 to 100000. In the native enzyme, 4.09 (±0.25) atoms of nickel per molecule were detected. The N-terminal amino acids of the urease subunits were identical to those from Staphylococcus xylosus, and amino acid analysis revealed high similarities in both enzymes; no cysteine was detected after acid hydrolysis of vinylpyridinylated urease. Electron micrographs of negatively stained urease specimens from both staphylococci showed identical size and structure.Abbreviation PAGE polyacrylamide gel electrophoresis