scholarly journals Proteasomal degradation of Saccharomyces cerevisiae Sup35p fibrils (negative-stained electron micrograph in the background) generates amyloidogenic peptides derived from its N-terminal prion domain (leading to the [PSI+] phenotype). For further details re

2014 ◽  
Vol 92 (3) ◽  
pp. i-i
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Proteasomal Degradation ◽  
Electron Micrograph ◽  
Amyloidogenic Peptides

scholarly journals Ccr4 is a novel shuttle factor required for ubiquitin-dependent proteolysis by the 26S proteasome

2020 ◽  
Author(s):  
Ganapathi Kandasamy ◽  
Ashis Kumar Pradhan ◽  
R Palanimurugan
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Degradation ◽  
Ubiquitin Proteasome System ◽  
Proteasomal Degradation ◽  
Rna Degradation ◽  
26S Proteasome ◽  
Cellular Proteins ◽  
Cellular Homeostasis ◽  
Substrate Degradation ◽  
Ubiquitin Proteasome

AbstractDegradation of short-lived and abnormal proteins are essential for normal cellular homeostasis. In eukaryotes, such unstable cellular proteins are selectively degraded by the ubiquitin proteasome system (UPS). Furthermore, abnormalities in protein degradation by the UPS have been linked to several human diseases. Ccr4 protein is a known component of the Ccr4-Not complex, which has established roles in transcription, mRNA de-adenylation and RNA degradation etc. Excitingly in this study, we show that Ccr4 protein has a novel function as a shuttle factor that promotes ubiquitin-dependent degradation of short-lived proteins by the 26S proteasome. Using a substrate of the well-studied ubiquitin fusion degradation (UFD) pathway, we found that its UPS-mediated degradation was severely impaired upon deletion of CCR4 in Saccharomyces cerevisiae. Additionally, we show that Ccr4 binds to cellular ubiquitin conjugates and the proteasome. In contrast to Ccr4, most other subunits of the Ccr4-Not complex proteins are dispensable for UFD substrate degradation. From our findings we conclude that Ccr4 functions in the UPS as a shuttle factor targeting ubiquitylated substrates for proteasomal degradation.

scholarly journals Pex3 confines pexophagy receptor activity of Atg36 to peroxisomes by regulating Hrr25-mediated phosphorylation and proteasomal degradation

2020 ◽  
Vol 295 (48) ◽  
pp. 16292-16298
Author(s):  
Sota Meguro ◽  
Xizhen Zhuang ◽  
Hiromi Kirisako ◽  
Hitoshi Nakatogawa
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Recombinant Proteins ◽  
Posttranslational Modifications ◽  
Membrane Vesicles ◽  
Proteasomal Degradation ◽  
Regulatory Mechanisms ◽  
Autophagosome Formation ◽  
Peroxisomal Membrane ◽  
Double Membrane ◽  
Selective Autophagy

In macroautophagy (hereafter autophagy), cytoplasmic molecules and organelles are randomly or selectively sequestered within double-membrane vesicles called autophagosomes and delivered to lysosomes or vacuoles for degradation. In selective autophagy, the specificity of degradation targets is determined by autophagy receptors. In the budding yeast Saccharomyces cerevisiae, autophagy receptors interact with specific targets and Atg11, resulting in the recruitment of a protein complex that initiates autophagosome formation. Previous studies have revealed that autophagy receptors are regulated by posttranslational modifications. In selective autophagy of peroxisomes (pexophagy), the receptor Atg36 localizes to peroxisomes by binding to the peroxisomal membrane protein Pex3. We previously reported that Atg36 is phosphorylated by Hrr25 (casein kinase 1δ), increasing the Atg36–Atg11 interaction and thereby stimulating pexophagy initiation. However, the regulatory mechanisms underlying Atg36 phosphorylation are unknown. Here, we show that Atg36 phosphorylation is abolished in cells lacking Pex3 or expressing a Pex3 mutant defective in the interaction with Atg36, suggesting that the interaction with Pex3 is essential for the Hrr25-mediated phosphorylation of Atg36. Using recombinant proteins, we further demonstrated that Pex3 directly promotes Atg36 phosphorylation by Hrr25. A co-immunoprecipitation analysis revealed that the interaction of Atg36 with Hrr25 depends on Pex3. These results suggest that Pex3 increases the Atg36–Hrr25 interaction and thereby stimulates Atg36 phosphorylation on the peroxisomal membrane. In addition, we found that Pex3 binding protects Atg36 from proteasomal degradation. Thus, Pex3 confines Atg36 activity to the peroxisome by enhancing its phosphorylation and stability on this organelle.

scholarly journals Impaired Cutinase Secretion in Saccharomyces cerevisiae Induces Irregular Endoplasmic Reticulum (ER) Membrane Proliferation, Oxidative Stress, and ER-Associated Degradation

2002 ◽  
Vol 68 (5) ◽  
pp. 2155-2160 ◽  
Author(s):  
C. M. J. Sagt ◽  
W. H. Müller ◽  
L. van der Heide ◽  
J. Boonstra ◽  
A. J. Verkleij ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Protein Aggregation ◽  
Fold Increase ◽  
Proteasomal Degradation ◽  
Wild Type ◽  
Unfolded Protein ◽  
Protein Response ◽  
And Oxidative Stress

ABSTRACT Impaired secretion of the hydrophobic CY028 cutinase invokes an unfolded protein response (UPR) in Saccharomyces cerevisiae cells. Here we show that the UPR in CY028-expressing S. cerevisiae cells is manifested as an aberrant morphology of the endoplasmic reticulum (ER) and as extensive membrane proliferation compared to the ER morphology and membrane proliferation of wild-type CY000-producing S. cerevisiae cells. In addition, we observed oxidative stress, which resulted in a 21-fold increase in carbonylated proteins in the CY028-producing S. cerevisiae cells. Moreover, CY028-producing S. cerevisiae cells use proteasomal degradation to reduce the amount of accumulated CY028 cutinase, thereby attenuating the stress invoked by CY028 cutinase expression. This proteasomal degradation occurs within minutes and is characteristic of ER-associated degradation (ERAD). Our results clearly show that impaired secretion of the heterologous, hydrophobic CY028 cutinase in S. cerevisiae cells leads to protein aggregation in the ER, aberrant ER morphology and proliferation, and oxidative stress, as well as a UPR and ERAD.

scholarly journals Proteasomal Degradation of Rpn4 in Saccharomyces cerevisiae Is Critical for Cell Viability Under Stressed Conditions

Genetics ◽  
2009 ◽  
Vol 184 (2) ◽  
pp. 335-342 ◽  
Author(s):  
Xiaogang Wang ◽  
Haiming Xu ◽  
Seung-Wook Ha ◽  
Donghong Ju ◽  
Youming Xie
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Viability ◽  
Proteasomal Degradation

Light Optical Diffraction Studies of Macromolecular Ultrastructure

1970 ◽  
Vol 28 ◽  
pp. 258-259
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Diffraction Analysis ◽  
Diffraction Pattern ◽  
Electron Micrographs ◽  
Optical Diffraction ◽  
Electron Micrograph ◽  
Its Analysis ◽  
Resolution Electron ◽  
Diffraction Patterns

Analysis of light optical diffraction patterns produced by electron micrographs can easily lead to much nonsense. Such diffraction patterns are referred to as optical transforms and are compared with transforms produced by a variety of mathematical manipulations. In the use of light optical diffraction patterns to study periodicities in macromolecular ultrastructures, a number of potential pitfalls have been rediscovered. The limitations apply to the formation of the electron micrograph as well as its analysis.(1) The high resolution electron micrograph is itself a complex diffraction pattern resulting from the specimen, its stain, and its supporting substrate. Cowley and Moodie (Proc. Phys. Soc. B, LXX 497, 1957) demonstrated changing image patterns with changes in focus. Similar defocus images have been subjected to further light optical diffraction analysis.

On an Application of the Metallurgical Stage to Chromosome Morphology

1967 ◽  
Vol 25 ◽  
pp. 28-29
Author(s):  
Godfrey C. Hoskins
Keyword(s):  
Human Chromosome ◽  
Electron Micrographs ◽  
Chromosome Morphology ◽  
Electron Optics ◽  
Electron Micrograph ◽  
Photographic Evidence ◽  
Sophisticated Equipment ◽  
Periodic Arrangement

The first serious electron microscooic studies of chromosomes accompanied by pictures were by I. Elvers in 1941 and 1943. His prodigious study, from the manufacture of micronets to the development of procedures for interpreting electron micrographs has gone all but unnoticed. The application of todays sophisticated equipment confirms many of the findings he gleaned from interpretation of images distorted by the electron optics of that time. In his figure 18 he notes periodic arrangement of pepsin sensitive “prickles” now called secondary fibers. In his figure 66 precise regularity of arrangement of these fibers can be seen. In his figure 22 he reproduces Siegbahn's first stereoscopic electron micrograph of chromosomes.The two stereoscopic pairs of electron micrographs of a human chromosome presented here were taken with a metallurgical stage on a Phillips EM200. These views are interpreted as providing photographic evidence that primary fibers (1°F) about 1,200Å thick are surrounded by secondary fibers (2°F) arranged in regular intervals of about 2,800Å in this metanhase human chromosome. At the telomere the primary fibers bend back on themselves and entwine through the center of each of each chromatid. The secondary fibers are seen to continue to surround primary fibers at telomeres. Thus at telomeres, secondary fibers present a surface not unlike that of the side of the chromosome, and no more susceptible to the addition of broken elements from other chromosomes.

Undecagold labeling of tRNA

1991 ◽  
Vol 49 ◽  
pp. 44-45
Author(s):  
James F. Hainfeld ◽  
Kyra M. Alford ◽  
Mathias Sprinzl ◽  
Valsan Mandiyan ◽  
Santa J. Tumminia ◽  
...  
Keyword(s):  
High Resolution ◽  
Transmission Electron Micrograph ◽  
Anticodon Loop ◽  
Electron Micrograph ◽  
Reaction Conditions ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The undecagold (Au11) cluster was used to covalently label tRNA molecules at two specific ribonucleotides, one at position 75, and one at position 32 near the anticodon loop. Two different Au11 derivatives were used, one with a monomaleimide and one with a monoiodacetamide to effect efficient reactions.The first tRNA labeled was yeast tRNAphe which had a 2-thiocytidine (s2C) enzymatically introduced at position 75. This was found to react with the iodoacetamide-Aun derivative (Fig. 1) but not the maleimide-Aun (Fig. 2). Reaction conditions were 37° for 16 hours. Addition of dimethylformamide (DMF) up to 70% made no improvement in the labeling yield. A high resolution scanning transmission electron micrograph (STEM) taken using the darkfield elastically scattered electrons is shown in Fig. 3.

Practical Picture Processing

1974 ◽  
Vol 32 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Radiation Damage ◽  
Coherence Length ◽  
Spatial Information ◽  
State Of The Art ◽  
Coherent Radiation ◽  
The State ◽  
Energy Spread ◽  
Electron Micrograph ◽  
Picture Processing ◽  
Molecular Skeleton

Various authors have emphasized the spatial information resident in an electron micrograph taken with adequately coherent radiation. In view of the completion of at least one such instrument, this opportunity is taken to summarize the state of the art of processing such micrographs. We use the usual symbols for the aberration coefficients, and supplement these with £ and 6 for the transverse coherence length and the fractional energy spread respectively. He also assume a weak, biologically interesting sample, with principal interest lying in the molecular skeleton remaining after obvious hydrogen loss and other radiation damage has occurred.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

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