Regulation fo protein kinase C activity by various lipids

Protein kinase C has recently attracted considerable attention because of its importance in the control of cell division, cell differentiation, and signal transduction across the cell membrane. The activity of this enzyme is altered by several lipids such as diacylglycerol, free fatty acids, lipoxins, gangliosides, and sulfatides. These lipids may interact with protein kinase C either directly or through calcium ions and produce their regulatory effect (activation or inhibition) on the activities of the enzymes phosphorylated by this kinase. These processes widen our perspective of the regulation of intercellular and intracelluular communication.Abbreviations used (PK-C) Protein kinase C - (cAMP-PK) cAMP dependent protein kinase - (DAG) diacylglycerol - (PtdSer) phosphatidylserine - (InsP ₃) inositol 1,4,5-trisphosphate - (PtdIns 4,5-P₂) inositol 4,5 bisphosphate - (FFA) free fatty acid - (MBP) myelin basic protein - (ATP) adenosine triphosphate - (GTP) guanine triphosphate - (TPA) 12-tetradecanoylphorbol-13-acetate - (EGF) epidermal growth factor - (PDGF) platelet derived growth factor - (NeuNAc) and N-acetylneuraminic acid     

Leader protein of foot-and-mouth disease virus is required for cleavage of the p220 component of the cap-binding protein complex.

Suppression of host protein synthesis in cells infected by poliovirus and certain other picornaviruses involves inactivation of the cap-binding protein complex. Inactivation of this complex has been correlated with the proteolytic cleavage of p220, a component of the cap-binding protein complex. Since picornaviral RNA is not capped, it continues to be translated as the cap-binding protein complex is inactivated. The cleavage of p220 can be induced to occur in vitro, catalyzed by extracts from infected cells or by reticulocyte lysates translating viral RNA. Expression of polioviral protease 2A is sufficient to induce p220 cleavage, and the presence in 2A of an 18-amino-acid sequence representing a putative cysteine protease active site correlates with the ability of different picornaviruses to induce p220 cleavage. Foot-and-mouth disease virus (FMDV) infection induces complete cleavage of p220, yet the FMDV genome codes for a 2A protein of only 16 amino acids, which does not include the putative cysteine protease active site. Using cDNA plasmids encoding various regions of the FMDV genome, we have determined that the leader protein is required to initiate p220 cleavage. This is the first report of a function for the leader protein, other than that of autocatalytic cleavage from the FMDV polyprotein.     

Molecular analysis of plasmid DNA repair within ultraviolet-irradiated Escherichia coli. I. T4 endonuclease V-initiated excision repair

The process by which DNA-interactive proteins locate specific sequences or target sites on cellular DNA within Escherichia coli is a poorly understood phenomenon. In this study, we present the first direct in vivo analysis of the interaction of a DNA repair enzyme, T4 endonuclease V, and its substrate, pyrimidine dimer-containing plasmid DNA, within UV-irradiated E. coli. A pyrimidine dimer represents a small target site within large domains of DNA. There are two possible paradigms by which endonuclease V could locate these small target sites: a processive mechanism in which the enzyme "scans" DNA for dimer sites or a distributive process in which dimers are located by random three-dimensional diffusion. In order to discriminate between these two possibilities in E. coli, an in vivo DNA repair assay was developed to study the kinetics of plasmid DNA repair and the dimer frequency (i.e. the number of dimer sites on a given plasmid molecule) in plasmid DNA as a function of time during repair. Our results demonstrate that the overall process of plasmid DNA repair initiated by T4 endonuclease V (expressed from a recombinant plasmid within repair-deficient E. coli) occurs by a processive mechanism. Furthermore, by reducing the temperature of the repair incubation, the endonuclease V-catalyzed incision step has been effectively decoupled from the subsequent steps including repair patch synthesis, ligation, and supercoiling. By this manipulation, it was determined that the overall processive mechanism is composed of two phases: a rapid processive endonuclease V-catalyzed incision reaction, followed by a slower processive mechanism, the ultimate product of which is the dimer-free supercoiled plasmid molecule.     

Identification of N-glycolylneuraminic acid-containing gangliosides of cat and sheep erythrocytes. 252Cf fission fragment ionization mass spectrometry in the analysis of glycosphingolipids

A number of gangliosides were isolated from cat and sheep erythrocytes for use in analyzing the specificity of a panel of human anti-heterophile monoclonal antibodies. The structures of these compounds were determined by a combination of different procedures, including sugar analysis, glycosidase treatment, periodate oxidation, TLC immunostaining, methylation analysis, and mass spectrometry. These methods identified the cat erythrocytes gangliosides (C1 and C2) as N-glycolylneuraminic acid (NeuGc)-containing hematosides; C1 was shown to be NeuGc alpha 2----8NeuGc alpha 2----3Gal beta I----4Glc-Cer [NeuGc)2GD3) and C2 to be NeuAc alpha 2----8NeuGc alpha 2----3Gal beta 1----4Glc-Cer [NeuAc-NeuGc-)GD3). The two sheep gangliosides (S1 and S2) were found to be novel glycolipids based on the paragloboside sequence; S1 was identified as NeuGc alpha 2----8NeuGc alpha 2----3Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4Glc-Cer [NeuGc)2-disialylparagloboside) and S2 as NeuAc alpha 2----8NeuGc alpha 2----3Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4Glc-Cer [NeuAc-NeuGc-)-disialylparagloboside). Structural analysis of these compounds was aided by the use of 252Cf fission fragment ionization time-of-flight mass spectrometry. This method provided easily interpretable spectra on methylated derivatives which were particularly useful in determining the sialic acid composition of the gangliosides and the sequence of their disialosyl side chains.     

A single base mutation in the gene for type III collagen (COL3A1) converts glycine 847 to glutamic acid in a family with Ehlers-Danlos syndrome type IV. An unaffected family member is mosaic for the mutation

Summary Ehlers-Danlos syndrome type IV, an inherited connective tissue disease, is usually caused by mutations in the gene for type III collagen. Here, we describe a glycine to glutamic acid substitution in a patient with this syndrome. Previous studies had shown that fibroblasts from the patient, his mother and brother secreted a reduced amount of type III collagen and also produced an overmodified form of the protein that was preferentially retained intracellularly. Peptide mapping experiments indicated that the mutation was located within cyanogen bromide peptide 9. This was supported by chemical cleavage analysis and sequencing of cDNA encoding this region. Allele-specific oligonucleotide hybridisation of genomic DNA confirmed that a G to A mutation converted Gly 847 to Glu. The mutation was present in two other affected family members and also in a third, who was clinically unaffected. Further analysis of this unaffected individual revealed reduced mutant:normal ratios in DNA obtained from both blood and hair samples, showing that she was mosaic for the mutation.     

Demographic responses of arctic hares Lepus arcticus placed on two predominantly forested islands in Newfoundland

During January-April 1989. we monitored survival, reproduction, and body condition of 19 radio-collared arctic hares Lepus areticus introduced to two predominantly (80%) forested islands. Merchant (66 1 ha) and Burke (82 6 ha), in Placentia Bay, Newfoundland By late April, bone-marrow fat (42 7%) and kidney fat indices were lower than found in populations on the mountain barrens of western Newfoundland However, most island hares gained weight overwinter, and litter sizes (mean. 4 2 in utero) and testis weights (mean, 8 3 g) were as large or larger than recorded from other introduced and natural populations in Newfoundland The distribution of telemetry locations, tracks and feeding sites indicated that hares frequented the scattered barrens (totalling c 30 ha) on both islands in greater proportion than available These results suggest that, in the absence of snowshoe hares and mammalian predators, forested regions interspersed with small patches of barrens can sustain arctic hares     

Evidence of abortive recombination in ruv mutants of Escherichia coli K12

Summary Genetic recombination in Escherichia coli was investigated by measuring the effect of mutations in ruv and rec genes on F-prime transfer and mobilization of nonconjugative plasmids. Mutation of ruv was found to reduce the recovery of F-prime transconjugants in crosses with recB recC sbcA strains by about 30-fold and with recB recC sbcB sbcC strains by more than 300-fold. Conjugative plasmids lacking any significant homology with the chromosome were transferred normally to these ruv mutants. Mobilization of the plasmid cloning vectors pHSG415, pBR322, pACYC184 and pUC18 were reduced by 20- to 100-fold in crosses with ruv rec ⁺ sbc ⁺ strains, depending on the plasmid used. Recombinant plasmids carrying ruv ⁺ were transferred efficiently. With both F-prime transfer and F-prime cointegrate mobilization, the effect of ruv was suppressed by inactivating recA. It is proposed that the failure to recover transconjugants in ruv recA ⁺strains is due to abortive recombination and that the ruv genes define activities which function late in recombination to help convert recombination intermediates into viable products.     

Enzyme activity in organic solvent as a function of water activity determined by membrane inlet mass spectrometry

Summary Membrane inlet mass spectrometry (MIMS) is introduced as a method for measuring water activity in nonpolar solvents, aqueous solutions and gas phase. The determination of the rate of hydrolysis of diphenyl carbonate by porcine liver esterase as a function of water activity in diisopropyl ether is presented as an example. A linear relationship is found between the enzyme activity and the water activity.     

Dichogamy,gender variation and bet-hedging inPseudowintera colorata

Summary Temporal patterns of variability in the longevity of the male and female phases of individual flowers and in the gender expression of plants of a dichogamous New Zealand tree,Pseudowintera colorata (Winteraceae), were documented in field studies. Two measures for the duration of phases in a dichogamous flower are distinguished; the nominal phases based on morphological features of the flower, and the effective phases reflecting the duration of their functions. Flower and phase longevity and phenotypic gender varied considerably throughout the season and among individuals. Temporal variability in phenotypic gender was loosely synchronized among the 12 plants sampled. Three effects of an environmental factor (temperature) were noted. First, increased temperatures shortened the duration of the female phase but had no effect on the duration of the male phase. Second, pollination frequency was positively correlated with temperature. These results indirectly suggest that increased pollination may shorten the duration of the female phase. Third, average population maleness, measured as the proportion of open flowers in the population on a given day which were in the male phase, was positively correlated with temperature. It is postulated that temperature indirectly influences temporal patterns of gender expression in the population through its differential effects on the longevity of the male and female phases in individual flowers. A theoretical model of bet-hedging shows that, if the direction of an environmental effect on the proportions of the sexual phases is irreversible, selection favours asynchronous dichogamy and reduces the temporal variability as much as possible. If the direction of the response is reversible, heterodichogamy is favoured.