Partial inhibition of protein synthesis accelerates the synthesis of porphyrin in heme-deficient mutants of Escherichia coli

Mutants of Escherichia coli defective in the HemA protein grow extremely poorly as the result of heme deficiency. A novel hemA mutant was identified whose rate of growth was dramatically enhanced by addition to the medium of low concentrations of translational inhibitors, such as chloramphenicol and tetracycline. This mutant (H110) carries mutation at position 314 in the hemA gene, which resulted in diminished activity of the encoded protein. Restoration of growth of H110 upon addition of the drugs mentioned above was due to activation of the synthesis of porphyrin. However, this activation was not characteristic exclusively of cells with this mutant hemA gene since it was also observed in a heme-deficient strain bearing the wild-type hemA gene. The activation did not depend on the promoter activity of the hemA gene, as indicated by studies with fusion genes. It appears that partial inhibition of protein synthesis via inhibition of peptidyltransferase can promote the synthesis of porphyrin by providing an increased supply of Guamyl-tRNA for porphyrin synthesis. Glutamyl-tRNA is the common substrate for peptidyltransferase and HemA.     

Mutual Contact of Adherent Polymorphonuclear Leukocytes Inhibits Their Generation of Superoxide

Superoxide generation by polymorphonuclear leukocytes (PMNs) in suspension, or adherent to glass or plastic, after stimulation with /V-formylmethionyl-leucyl-phenylalanine or phorbol myristate acetate was measured by cytochromec reduction and spin trapping. Amounts of superoxide generated by adherent PM Ns were inversely related to cell density. The generation of hydrogen peroxide was also inhibited at higher cell densities. In contrast to adherent cells, superoxide released by PMNs in suspension linearly increased with respect to cell number over a wider range. Microscopic observation indicated that the number of cells in mutual contact increased rapidly at cell densities higher than 4 × 10⁴ cells/cm², and inhibition of superoxide became apparent at higher cell densities. Mediators which could be released by PMNs, such as NO and adenosine, were not the cause of inhibition. Thesedatu suggest that mutual contact of PMNs suppresses their generation of superoxide. Survival rates of PMNs after stimulation increased at higher densities, indicating that the mutual contact-induced inhibition of superoxide generation by PMNs may be physiologically relevant at sites of inflammation.     

Keratinocyte growth factor

Keratinocyte growth factor (KGF) is a member of the heparin-binding fibroblast growth factor family (FGF-7) with a distinctive pattern of target-cell specificity. Studies performed in cell culture suggested that KGF was mitogenically active only on epithelial cells, albeit from a variety of tissues. In contrast, KGF was produced solely by cells of mesenchymal origin, leading to the hypothesis that it might function as a paracrine mediator of mesenchymal-epithelial communication. Biochemical analysis and molecular cloning established that the KGF receptor (KGFR) was a tyrosine kinase isoform encoded by the fgfr-2 gene. Many detailed investigations of KGF and KGFR expression in whole tissue and cell lines largely substantiated the pattern initially perceived in vitro of mesenchymal and epithelial distribution, respectively. Moreover, functional assays in organ culture and in vivo and studies of KGF regulation by sex sterorid hormones reinforced the idea that KGF acts predominantly on epithelial cells to elicit a variety of responses including proliferation, migration and morphogenesis.     

Nucleotide Sequence Surrounding the Locus Marker D21S246 on Human Chromosome 21

Most ofthe human Not I linking clones identified to date areconsidered to be derived from CpG islands because ofthe recognitionsequence of this enzyme, and CpG islands have been reportedto be located around the 5' regions of genes. As a pilot study,we determined the complete nucleotide sequence (41,924 bp) ofa human cosmid clone (LL21NC02Q7A10) containing the marker D21S246originating from a Not I linking clone. As a result of sequenceanalysis, we successfully mapped and revealed the genomic genestructure for KIAA0002 previously reported as a cDNA clone.This gene consists of 15 exons and was shown to exist at theD21S246 locus on human chromosome 21q21.3–q22.1. Theseresults demonstrated that genomic marker-anchored DNA sequencingis a useful approach for the human genome project.     

Mutation analysis of the cellulose-binding domain of the Clostridium cellulovorans cellulose-binding protein A.

Cellulose-binding protein A (CbpA) has been previously shown to mediate the interaction between crystalline cellulose substrates and the cellulase enzyme complex of Clostridium cellulovorans. CbpA contains a family III cellulose-binding domain (CBD) which, when expressed independently, binds specifically to crystalline cellulose. A series of N- and C-terminal deletions and a series of small internal deletions of the CBD were created to determine whether the entire region previously described as a CBD is required for the cellulose-binding function. The N- and C-terminal deletions reduced binding affinity by 10- to 100-fold. Small internal deletions of the CBD resulted in substantial reduction of CBD function. Some, but not all, point mutations throughout the sequence had significant disruptive effects on the binding ability of the CBD. Thus, mutations in any region of the CBD had effects on the binding of the fragment to cellulose. The results indicate that the entire 163-amino-acid region of the CBD is required for maximal binding to crystalline cellulose.     

Production of poly(3-hydroxyalkanoates-co-3-hydroxy-ω-fluoroalkanoates) byPseudomonas oleovorans from 1-fluorononane and gluconate

Summary Pseudomonas oleovorans grew well and synthesized copolyesters of 3-hydroxyalkanoates and 3-hydroxy--fluoroalkanoates in the mineral medium containing 1-fluorononane and sodium gluconate. The content of fluorinated units in copolyesters could be controlled from 0 to 40 mol%. The copolyesters were shown to have a random sequence distribution of different monomeric units by analysis of the¹³C NMR spectra. The melting temperatures of copolyesters were 52–58°C, and the enthalpy of fusion decreased with the content of fluorinated units.     

Staining method of poly(3-hydroxyalkanoic acids) producing bacteria by nile blue

Summary Using an ethanol solution of nile blue, we have developed an efficient method to detect the colonies of poly(3-hydroxyalkanoic acids) (PHA) producing bacteria on the agar plate. When the bacterial colonies with PHA granules were stained with nile blue, the stained colonies fluoresced bright orange on the irradiation of UV light. In the fluoresce emission spectra, fluorescence intensity increased with an increase in the PHA content of bacterial cells.Alcaligenes eutrophus andA.latus colonies with poly(3-hydroxybutyric acid) (PHB) homopolymer exhibited an emission maximum at 580nm on the excitation at 490nm. On the other hand,Pseudomonas oleovorans andP.putida with medium-chain-length (mcl-) PHA copolymers of C6, C8 and C10 units exhibited an emission maximum at 570nm.     

Global bifurcation structure of a Bonhoeffer-van der Pol oscillator driven by periodic pulse trains

The Bonhoeffer-van der Pol (BVP) oscillator is a valuable dynamical system model of pacemaker neurons. Isochrons, phase transition curves (PTC), and two dimensional bifurcation diagrams served to analyze the neuron's response to periodic pulse stimuli. Responses are described and explained in terms of the nonlinear dynamical system theory. An important issue in the generation of spikes by pacemaker neurons is the existence of both slow and fast dynamics in the state point's trajectory in the phase plane. It is this feature in particular that makes the BVP oscillator a faithful model of living pacemaker neurons. Comparison of the model's responses with those of a living pacemaker was based also on return maps of interspike intervals. Analyzed in detail were the complex discharges called stammering which involve interspike intervals that arise unpredictably and exhibit histograms with several modes separated by the equal intervals.Supported by Trent H. Wells Jr. Inc.