Interaction of DNA with DNA binding proteins. III. Infectivity of protein-complexed phage fd DNA in Escherichia coli spheroplasts.

Complex formation of circular, single-stranded phage fd DNA with Escherichia coli DNA binding protein HD or phage fd gene 5 protein keeps infection of E. coli spheroplasts at the level of free phage DNA, whereas complexes of this DNA with E. coli DNA unwinding protein show a strongly reduced efficiency of transfection. Displacement of the unwinding protein by HD protein or gene 5 protein also maintains the poor adsorption of the complexes to spheroplasts. Free E. coli DNA unwinding protein and residual amounts of this protein bound to the DNA may interfere with the adsorption and the uptake of the phage genome.     

Enzymatic amidation of recombinant (Leu27) growth hormone releasing hormone-Gly45

By chemoenzymatic synthesis the gene for a (Leu27) analogue of human growth hormone releasing hormone-Gly45 [(Leu27)GHRH-Gly45] was constructed, cloned and expressed in Escherichia coli as a fusion protein with beta-galactosidase under the control of the lac promoter and operator. Upon induction with isopropyl-D-thio-beta-galactopyranoside the fusion protein accumulated to a yield of 15-20% of the total cellular protein. After cyanogen bromide cleavage of the fusion protein the precursor peptide (Leu27)hGHRH-Gly45 was separated by extraction and purified by ion exchange and h.p.l.c.-RP18 chromatography. The purified peptide was analysed by sequencing, isoelectric focusing, amino acid analysis and amino acid analysis after V8 protease digestion. The carboxy-terminal glycine was subsequently amidated by PAM (peptidylglycine-alpha-amidating-monooxygenase), an enzyme which was isolated and characterized from fresh bovine pituitaries. Correct amidation of the penultimate amino acid, leucine, was verified by peptide sequencing with an authentic leucine amide reference.     

Understanding of elderly patients' resuscitation preferences by physicians and nurses.

We compared the understanding by family physicians and nurses of their elderly outpatients'' preferences for cardiopulmonary resuscitation and mechanical ventilation under 3 scenarios reflecting varying qualities of life. Physicians and nurses correctly predicted patients'' treatment preferences in from 59% to 84% and 53% to 78% of cases, respectively, for the various decisions. For most decisions, neither physicians nor nurses were significantly more accurate in their predictions than expected by chance alone. Moreover, nurses and physicians did not significantly agree with one another in their predictions of patients'' preferences for any of these decisions. These results suggest that while nurses'' and physicians'' perceptions of patients'' preferences for life-sustaining treatment are not necessarily similar, neither nurses nor physicians systematically understand their elderly patients'' resuscitation preferences.     

Stereospecific production of the herbicide phosphinothricin (glufosinate) by transamination: cloning, characterization, and overexpression of the gene encoding a phosphinothricin-specific transaminase from Escherichia coli

We have cloned the gene encoding a 43-kilodalton transaminase from Escherichia coli K-12 with a specificity for L-phosphinothricin [L-homoalanine-4-yl-(methyl)phosphinic acid], the active ingredient of the herbicide Basta (Hoechst AG). The structural gene was isolated, together with its own promoter, and shown to be localized on a 1.6-kilobase DraI-BamHI fragment. The gene is subject to catabolite repression by glucose; however, repression could be relieved completely when 4-aminobutyrate (GABA) served as the sole nitrogen source. The regulation pattern obtained and a comparison of the restriction map of the initially cloned 15-kilobase SalI fragment with the physical map of the E. coli K-12 genome suggest that the cloned gene is identical with gabT, a locus on the gab gene cluster of E. coli K-12 which codes for the GABA:2-ketoglutartate transaminase (EC 2.6.1.19). A number of expression plasmids carrying the isolated transaminase gene were constructed. With these constructs, the transaminase expression in transformants of E. coli could be increased up to 80-fold compared with that in a wild-type control, and the transaminase constituted up to 20% of the total soluble protein of the bacteria. Thus, the protein crude extracts of the transformants could be used, after a simple heat precipitation step, for the biotechnological production of L-phosphinothricin in an enzyme reactor.     

Expression of bovine adrenodoxin in E. coli and site-directed mutagenesis of /2 Fe-2S/ cluster ligands.

Expression systems for adrenodoxin into the periplasm and the cytoplasm of E. coli have been developed as a prerequisite for site-directed mutagenesis studies. In both systems the /2Fe-2S/ cluster of the protein was correctly assembled, the cytoplasmic one gives, however, a tenfold higher expression level. To determine which of the five cysteines at positions 46, 52, 55, 92, and 95 coordinate the /2Fe-2S/ center, they have been individually mutated into serines. From these mutants, only C95S forms a functionally active holoprotein. Thus, residues 46, 52, 55, and 92 are the cysteines that coordinate the /2Fe-2S/ cluster in adrenodoxin.     

Limnology and performance of waste treatment lagoons

By arranging sewage ponds in series, some feedback relationships within the food web are disconnected, but stability may increase. This particularly applies to a persistent clearwater-state in the last cell caused by mass growths of Daphnia or other zooplankton in the absence of fish. Microbial pollution in this case is reduced to a level which may permit nearly unrestricted irrigation. The oxygen balance of lagoons is, apart from the diurnal cycle, subject to substantial temporal variations. This also applies to continuous-flow laboratory models with a constant (BOD-load, temperature) or a constant-cycle (light) chemical and physical environment. An example is given illustrating a high adjustment stability of a lagoon in consequence of a catastrophic perturbation.The strong tendency of lagoons towards an oligomictic behaviour is promoted by thermal stratification and by a vertical gradient in the metabolic activity (oxidation/reduction potential). The hydrodynamic conditions oscillate between plug flow in periods of convective overturn and short-circuiting if thermal stratification has developed. Nevertheless, the average performance (BOD removal) for a particular season could be calculated with a reasonable accuracy. As a basis for this calculation, nomographs were developed from which the rate coefficient K₁ of BOD removal for a given combination of residence time and BOD load can be read.     

Enhanced Specificity of Minimally Modified Anti-c-myc Oligonucleotides

Abstract

The sequence-specificity of antisense oligonucleotides (ODN) against c-myc mRNA was tested by Northern blot analysis. Rat smooth muscle cells were treated with antisense or control ODN against c-myc modified by the “minimal protection strategy”. At 0.3 μM concentration the ODN show a very specific reduction in c-myc mRNA levels. Use of the “minimal protection strategy” minimizes nonspecific effects as observed for all-phosphorothioate ODN containing four consecutive guanine residues.     

An Eco1-independent sister chromatid cohesion establishment pathway in S. cerevisiae

Cohesion between sister chromatids, mediated by the chromosomal cohesin complex, is a prerequisite for their alignment on the spindle apparatus and segregation in mitosis. Budding yeast cohesin first associates with chromosomes in G1. Then, during DNA replication in S-phase, the replication fork-associated acetyltransferase Eco1 acetylates the cohesin subunit Smc3 to make cohesin’s DNA binding resistant to destabilization by the Wapl protein. Whether stabilization of cohesin molecules that happen to link sister chromatids is sufficient to build sister chromatid cohesion, or whether additional reactions are required to establish these links, is not known. In addition to Eco1, several other factors contribute to cohesion establishment, including Ctf4, Ctf18, Tof1, Csm3, Chl1 and Mrc1, but little is known about their roles. Here, we show that each of these factors facilitates cohesin acetylation. Moreover, the absence of Ctf4 and Chl1, but not of the other factors, causes a synthetic growth defect in cells lacking Eco1. Distinct from acetylation defects, sister chromatid cohesion in ctf4Δ and chl1Δ cells is not improved by removing Wapl. Unlike previously thought, we do not find evidence for a role of Ctf4 and Chl1 in Okazaki fragment processing, or of Okazaki fragment processing in sister chromatid cohesion. Thus, Ctf4 and Chl1 delineate an additional acetylation-independent pathway that might hold important clues as to the mechanism of sister chromatid cohesion establishment.