scholarly journals Membrane Association of the Escherichia coli Enterobactin Synthase Proteins EntB/G, EntE, and EntF

2000 ◽  
Vol 182 (6) ◽  
pp. 1768-1773 ◽  
Author(s):  
Feras M. Hantash ◽  
Charles F. Earhart
Keyword(s):  
Escherichia Coli ◽  
Final Stage ◽  
Membrane Fraction ◽  
Osmotic Shock ◽  
Buoyant Density ◽  
Membrane Association ◽  
Cytosolic Proteins ◽  
Outer Membranes ◽  
Cytoplasmic Proteins ◽  
A Minor

ABSTRACT The cytosolic proteins EntE, EntF, and EntB/G, which areEscherichia coli enzymes necessary for the final stage of enterobactin synthesis, are released by osmotic shock. Here, consistent with the idea that cytoplasmic proteins found in shockates have an affinity for membranes, a small fraction of each was found in membrane preparations. Two procedures demonstrated that the enzymes were enriched in a minor membrane fraction of buoyant density intermediate between that of cytoplasmic and outer membranes, providing indirect support for the notion that these proteins have a role in enterobactin excretion as well as synthesis.

scholarly journals The effects of polydisperse crowders on the compaction of the Escherichia coli nucleoid

2019 ◽  
Author(s):  
Da Yang ◽  
Jaana Männik ◽  
Scott T. Retterer ◽  
Jaan Männik
Keyword(s):  
Escherichia Coli ◽  
Cell Growth ◽  
Cell Membrane ◽  
Significant Contribution ◽  
Osmotic Shock ◽  
Dominant Role ◽  
Dna Binding Proteins ◽  
Bacterial Dna ◽  
E Coli ◽  
Cytoplasmic Proteins

ABSTRACTDNA binding proteins, supercoiling, macromolecular crowders, and transient DNA attachments to the cell membrane have all been implicated in the organization of the bacterial chromosome. However, it is unclear what role these factors play in compacting the bacterial DNA into a distinct organelle-like entity, the nucleoid. By analyzing the effects of osmotic shock and mechanical squeezing on Escherichia coli, we show that macromolecular crowders play a dominant role in the compaction of the DNA into the nucleoid. We find that a 30% increase in the crowder concentration from physiological levels leads to a 3-fold decrease in the nucleoid’s volume. The compaction is anisotropic, being higher along the long axes of the cell at low crowding levels. At higher crowding levels the compression becomes isotropic, implying that E. coli nucleoids lack a well-defined backbone. We furthermore show that the compressibility of the nucleoid is not significantly affected by cell growth rates and by prior treatment with rifampicin. The latter results point out that in addition to poly-ribosomes, soluble cytoplasmic proteins have a significant contribution in determining the size of the nucleoid.

scholarly journals Long-Term Experimental Evolution in Escherichia coli. IV. Targets of Selection and the Specificity of Adaptation

Genetics ◽  
1996 ◽  
Vol 143 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Michael Travisano ◽  
Richard E Lenski
Keyword(s):  
Escherichia Coli ◽  
Experimental Evolution ◽  
Common Ancestor ◽  
The Novel ◽  
Physiological Mechanisms ◽  
Outer Membranes ◽  
Limiting Nutrient ◽  
Novel Environments ◽  
Uptake Mechanisms

Abstract This study investigates the physiological manifestation of adaptive evolutionary change in 12 replicate populations of Escherichia coli that were propagated for 2000 generations in a glucose-limited environment. Representative genotypes from each population were assayed for fitness relative to their common ancestor in the experimental glucose environment and in 11 novel single-nutrient environments. After 2000 generations, the 12 derived genotypes had diverged into at least six distinct phenotypic classes. The nutrients were classified into four groups based upon their uptake physiology. All 12 derived genotypes improved in fitness by similar amounts in the glucose environment, and this pattern of parallel fitness gains was also seen in those novel environments where the limiting nutrient shared uptake mechanisms with glucose. Fitness showed little or no consistent improvement, but much greater genetic variation, in novel environments where the limiting nutrient differed from glucose in its uptake mechanisms. This pattern of fitness variation in the novel nutrient environments suggests that the independently derived genotypes adapted to the glucose environment by similar, but not identical, changes in the physiological mechanisms for moving glucose across both the inner and outer membranes.

scholarly journals Metallo-enzymes Released from Escherichia coli by Osmotic Shock

1968 ◽  
Vol 243 (10) ◽  
pp. 2647-2653 ◽  
Author(s):  
H F Dvorak ◽  
L A Heppel
Keyword(s):  
Escherichia Coli ◽  
Osmotic Shock

scholarly journals Ultrastructural and Biophysical Characterization of Hepatitis C Virus Particles Produced in Cell Culture

2010 ◽  
Vol 84 (21) ◽  
pp. 10999-11009 ◽  
Author(s):  
Pablo Gastaminza ◽  
Kelly A. Dryden ◽  
Bryan Boyd ◽  
Malcolm R. Wood ◽  
Mansun Law ◽  
...  
Keyword(s):  
Cell Culture ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Structural Characteristics ◽  
Buoyant Density ◽  
Hcv Rna ◽  
Membrane Bilayer ◽  
Biophysical Characterization ◽  
Negative Stain ◽  
A Minor

ABSTRACT We analyzed the biochemical and ultrastructural properties of hepatitis C virus (HCV) particles produced in cell culture. Negative-stain electron microscopy revealed that the particles were spherical (∼40- to 75-nm diameter) and pleomorphic and that some of them contain HCV E2 protein and apolipoprotein E on their surfaces. Electron cryomicroscopy revealed two major particle populations of ∼60 and ∼45 nm in diameter. The ∼60-nm particles were characterized by a membrane bilayer (presumably an envelope) that is spatially separated from an internal structure (presumably a capsid), and they were enriched in fractions that displayed a high infectivity-to-HCV RNA ratio. The ∼45-nm particles lacked a membrane bilayer and displayed a higher buoyant density and a lower infectivity-to-HCV RNA ratio. We also observed a minor population of very-low-density, >100-nm-diameter vesicular particles that resemble exosomes. This study provides low-resolution ultrastructural information of particle populations displaying differential biophysical properties and specific infectivity. Correlative analysis of the abundance of the different particle populations with infectivity, HCV RNA, and viral antigens suggests that infectious particles are likely to be present in the large ∼60-nm HCV particle populations displaying a visible bilayer. Our study constitutes an initial approach toward understanding the structural characteristics of infectious HCV particles.

scholarly journals Ecological Effects of Perorally Administered Pivmecillinam on the Normal Vaginal Microflora

2005 ◽  
Vol 49 (1) ◽  
pp. 170-175 ◽  
Author(s):  
Åsa Sullivan ◽  
Aino Fianu-Jonasson ◽  
Britt-Marie Landgren ◽  
Carl Erik Nord
Keyword(s):  
Escherichia Coli ◽  
Candida Albicans ◽  
Antimicrobial Agents ◽  
Ecological Impact ◽  
Menstrual Cycles ◽  
The Third ◽  
Vaginal Microflora ◽  
Normal Microflora ◽  
Facultative Anaerobic ◽  
A Minor

ABSTRACT The knowledge of the effects of antimicrobial agents on the normal vaginal microflora is limited. The objective of the present study was to study the ecological impact of pivmecillinam on the normal vaginal microflora. In 20 healthy women, the estimated day of ovulation was determined during three subsequent menstrual cycles. Microbiological and clinical examinations were performed on the estimated day of ovulation and on day 3 in all cycles and also on day 7 after ovulation in cycles 1 and 2. Anaerobic and facultative anaerobic gram-positive rods, mainly species of lactobacilli and actinomycetes, dominated the microflora. One woman was colonized on the third day of administration with a resistant Escherichia coli strain, and Candida albicans was detected in one woman on days 3 and 7 in cycle 2. No other major changes in the normal microflora occurred during the study. Administration of pivmecillinam had a minor ecological impact on the normal vaginal microflora.

Herpes simplex virus type 2 UL14 gene product has heat shock protein(HSP)-like functions

2002 ◽  
Vol 115 (12) ◽  
pp. 2517-2527
Author(s):  
Yohei Yamauchi ◽  
Kaoru Wada ◽  
Fumi Goshima ◽  
Tohru Daikoku ◽  
Kenzo Ohtsuka ◽  
...  
Keyword(s):  
Heat Shock ◽  
Nuclear Translocation ◽  
Osmotic Shock ◽  
Minor Component ◽  
Firefly Luciferase ◽  
Hsp70 Family ◽  
Arginine Residues ◽  
Simplex Virus ◽  
A Minor ◽  
Shock Proteins

The HSV-2 UL14 gene encodes a 32 kDa protein that is a minor component of the viral tegument. The protein relocates other viral proteins such as VP26 and UL33 protein into the nuclei of transiently coexpressing cells(Yamauchi et al., 2001). We found that the protein shared some characteristics of heat shock proteins(HSPs) or molecular chaperones, such as nuclear translocation upon heat shock,ATP deprivation and osmotic shock. Interestingly, a significant homology over a stretch of 15 amino acids was found between an N-terminal region of HSV UL14 protein and the substrate-binding domain of Hsp70 family proteins. Two arginine residues in this region were important for nuclear translocation of VP26. In addition, overexpression of UL14 protein increased the activity of coexpressed firefly luciferase, which suggested that the protein functioned in the folding of newly synthesized luciferase. We thus conclude that UL14 protein can act as a chaperone-like protein in a singly expressed state.

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