Enzymatic synthesis of 2-amino- 3-hydroxy-1,6-hexanedicar☐ylic acid using serinehydroxymethyltransferase

The scale up of earlier work from these laboratories using the enzyme serinehydroxymethyltransferase has resulted in the use of this enzyme for the synthesis of 2-amino-3-hydroxy-1,6-hexanedicar☐ylic acid (7) on a preparative scale. This compound, which has been barely described in the literature, is potentially useful for the synthesis of carbocyclic β-lactams and carbocyclic nucleosides.     

1H, 15N and 13C resonance assignments and secondary structure determination of the RNA-binding domain of E. coli rho protein

Summary Protein fragments containing the RNA-binding domain of Escherichia coli rho protein have been over-expressed in E. coli. NMR spectra of the fragment containing residues 1–116 of rho protein (Rho116) show that a region of this protein is unfolded in solution. Addition of (dC)₁₀ to this fragment stabilizes the folded form of the protein. The fragment comprising residues 1–130 of rho protein (Rho130) is found to be stably folded, both in the absence and presence of nucleic acid. NMR studies of the complex of Rho 130 with RNA and DNA oligonucleotides indicate that the binding-site size, affinity, and specificity of Rho 130 are similar to those of intact rho protein; therefore, Rho 130 is a suitable model of the RNA-binding domain of rho protein. NMR line widths as well as titration experiments of Rho130 complexed with oligonucleotides of various lengths suggest that Rho130 forms oligomers in the presence of longer oligonucleotides. ¹H, ¹⁵N and ¹³C resonance assignments were facilitated by the utilization of two pulse sequences, CN-NOESY and CCH-TOCSY. The secondary structure of unliganded Rho130 has been determined by NMR techniques, and it is clear that the RNA-binding domain of rho is more structurally similar to the cold shock domain than to the RNA recognition motif.Abbreviations Rho116, Rho130 protein containing the first 116 (130) residues of rho - CSD cold shock domain - RRM RNA recognition motif - RBD RNA-binding domain - IPTG isopropyl -D-thiogalactopyranoside - EDTA ethylenediaminetetraacetic acid - NOE nuclear Overhauser enhancement     

Non-linearities, synergisms and plant extinctions in South African fynbos and Australian kwongan

This paper explores the determinants of extinction of endemic plant taxa in mediterranean-climate regions in South Africa and southwestern Australia. Major threats to biodiversity in these areas include agriculture, deforestation, fragmentation, invasive alien organisms and urbanization. Case studies from the two regions show that synergisms between factors can lead to discontinuous, or non-linear, responses that have increased extinction rates (or threaten to) beyond predictions based on simple deterministic processes.     

Goats and garbage in Khartoum,Sudan: A study of the urban ecology of animal keeping

Waste management in developing world urban areas is an acute problem which is linked to high growth rates and abatement methods less advanced than in the developed world. Existing neighborhood waste management practices often include the use of organic waste as a feed supplement for urban livestock (mainly goats, but also sheep and cattle). These urban animals bring economic benefits to less affluent residents, who would suffer an economic loss if their supply of urban waste was reduced or eliminated by an organized waste collection and disposal strategy. This paper employs a survey of 319 Greater Khartoum households to derive an estimate of waste intake per urban animal, and illustrate demographic factors (e.g., rural or urban roots, income, education, number of children) which influence animal keeping. A loglinear/logit model is developed to predict animal-keeping households. This model can be applied by waste management planners to estimate the frequency of urban animals in developing world urban areas.     

Preparation and structure of heparin lyase-derived heparan sulfate oligosaccharides

Porcine intestinal mucosal heparan sulfate was exhaustivelydepolymerized on a large scale using beparin lyase II (heparinaseII) or heparin lyase III (heparitinase, EC 4.2.2.8 [EC] ). The oligosaccharidemixtures formed with each enzyme were fractionated by low pressuregel permeation chromatography. Size-uniform mixtures of disaccharides,tetrasaccharides, and hexasaccharides were obtained. Each size-fractionatedmixture was then purified on the basis of charge by repetitivesemipreparative strong-anion-exchange high-performance liquidchromatography. This approach has led to the isolation of 13homogenous oligosaccharides. The purity of each oligosaccharidewas demonstrated by the presence of a single peak on analyticalstrong-anion-exchange high-performance liquid chromatographyand reversed polarity capillary electrophoresis. The structuresof these oligosaccharides were established using 500 MHz one-and two-dimensional nuclear magnetic resonance spectroscopy.Three of the thirteen structures that were solved were novelwhile the remaining 10 have been previously described. All ofthe structures obtained using heparin lyase III contained a     

Artificial mutations and natural variations in the CD46 molecules from human and monkey cells define regions important for measles virus binding.

CD46 was previously shown to be a primate-specific receptor for the Edmonston strain of measles virus. This receptor consists of four short consensus regions (SCR1 to SCR4) which normally function in complement regulation. Measles virus has recently been shown to interact with SCR1 and SCR2. In this study, receptors on different types of monkey erythrocytes were employed as "natural mutant proteins" to further define the virus binding regions of CD46. Erythrocytes from African green monkeys and rhesus macaques hemagglutinate in the presence of measles virus, while baboon erythrocytes were the least efficient of the Old World monkey cells used in these assays. Subsequent studies demonstrated that the SCR2 domain of baboon CD46 contained an Arg-to-Gln mutation at amino acid position 103 which accounted for reduced hemagglutination activity. Surprisingly, none of the New World monkey erythrocytes hemagglutinated in the presence of virus. Sequencing of cDNAs derived from the lymphocytes of these New World monkeys and analysis of their erythrocytes with SCR1-specific polyclonal antibodies indicated that the SCR1 domain was deleted in these cells. Additional experiments, which used 35 different site-specific mutations inserted into CD46, were performed to complement the preceding studies. The effects of these artificial mutations were documented with a convenient binding assay using insect cells expressing the measles virus hemagglutinin. Mutations which mimicked the change found in baboon CD46 or another which deleted the SCR2 glycosylation site reduced binding substantially. Another mutation which altered GluArg to AlaAla at positions 58 and 59, totally abolished binding. Finally, the epitopes for two monoclonal antibodies which inhibit measles virus attachment were mapped to the same regions implicated by mutagenesis.