Mitochondria Tether Protein Trash to Rejuvenate Cellular Environments

Protein damage segregates asymmetrically in dividing yeast cells, rejuvenating daughters at the expense of mother cells. Zhou et al. now show that newly synthesized proteins are particularly prone to aggregation and describe a mechanism that tethers aggregated proteins to mitochondria. This association constrains aggregate mobility, effectively retaining and sorting toxic aggregates away from younger cells

The Escherichia coli trigger factor

AbstractE. coli trigger factor is an abundant cytosolic protein originally iDAntified by its ability to maintain the precursor of a secretory protein in a translocation competent form. Recent studies shed new light on the function of this protein. Trigger factor was found to be a peptidyl-prolyl-cisltrans-isomerase capable of catalysing protein folding in vitro, to associate with nascent cytosolic and secretory polypeptiDA chains, and to cooperate with the GroEL chaperone in promoting proteolysis of an unstable polypeptiDA in vivo. These findings suggest roles for trigger factor in various folding processes of secretory as well as cytosolic proteins

Unscrambling an egg: protein disaggregation by AAA+ proteins

A protein quality control system, consisting of molecular chaperones and proteases, controls the folding status of proteins and prevents the aggregation of misfolded proteins by either refolding or degrading aggregation-prone species. During severe stress conditions this protection system can be overwhelmed by high substrate load, resulting in the formation of protein aggregates. In such emergency situations, Hsp104/ClpB becomes a key player for cell survival, as it has the extraordinary capacity to rescue proteins from an aggregated state in cooperation with an Hsp70 chaperone system. The ring-forming Hsp104/ClpB chaperone belongs to the AAA+ protein superfamily, which in general drives the assembly and disassembly of protein complexes by ATP-dependent remodelling of protein substrates. A disaggregation activity was also recently attributed to other eubacterial AAA+ proteins, while such an activity has not yet been identified in mammalian cells. In this review, we report on new insights into the mechanism of protein disaggregation by AAA+ proteins, suggesting that these chaperones act as molecular crowbars or ratchets

Low temperature or GroEL/ES overproduction permits growth of Escherichia coli cells lacking trigger factor and DnaK

AbstractEscherichia coli trigger factor (TF) and DnaK cooperate in the folding of newly synthesized proteins. The combined deletion of the TF-encoding tig gene and the dnaK gene causes protein aggregation and synthetic lethality at 30°C. Here we show that the synthetic lethality of ΔtigΔdnaK52 cells is abrogated either by growth below 30°C or by overproduction of GroEL/GroES. At 23°C ΔtigΔdnaK52 cells were viable and showed only minor protein aggregation. Overproduction of GroEL/GroES, but not of other chaperones, restored growth of ΔtigΔdnaK52 cells at 30°C and suppressed protein aggregation including proteins ≥60 kDa, which normally require TF and DnaK for folding. GroEL/GroES thus influences the folding of proteins previously identified as DnaK/TF substrates

Poly-L-lysine enhances the protein disaggregation activity of ClpB

AbstractThe Hsp100 protein ClpB is a member of the AAA+ protein family that mediates the solubilization of aggregated proteins in cooperation with the DnaK chaperone system. Unstructured polypeptides such as casein or poly-L-lysine have been shown to stimulate the ATPase activity of ClpB and thus may both act as substrates. Here we compared the effects of α-casein and poly-L-lysine on the ATPase and chaperone activities of ClpB. α-Casein stimulated ATP hydrolysis by both AAA domains of ClpB and inhibited the ClpB-dependent solubilization of aggregated proteins if present in excess. In contrast, poly-L-lysine stimulated exclusively the ATPase activity of the second AAA domain and increased the disaggregation activity of ClpB. Thus poly-L-lysine does not act as substrate, but rather represents an effector molecule, which enhances the chaperone activity of ClpB

Kinders as slagoffers van seksuele misdade

Text in AfrikaansIn this dissertation the legal position with regard to children as victims of sexual crimes is examined in South Africa, England, Canada, Australia and New Zealand. Sexual crimes with children are a serious and widespread international problem. The purpose of this study is to identify deficiencies / gaps in the South African law. Children are not only the victims of the sexual crimes, but they are exposed to further trauma whilst giving evidence. Their best interests are also often not taken into proper consideration during the sentencing phase. In is in the interest of justice that children=s interests must be taken into account the whole time. In terms of international conventions and charters State parties are required to protect children against all forms of discrimination, violence, abuse and exploitation. Children may not be exposed to any sexual crimes, because these activities violate their right to bodily (and psychological) integrity, human dignity and privacy. In order to acknowledge the importance of children=s best interest, priority must be given to all cases in which children are the victims and their unique characteristics, age and development must be taken into consideration. This will ensure that they are not further victimized during the trial. Deficiencies in the Criminal Law are addressed by proposing new definitions, for instance for rape and incest. Shortcomings in the Procedural Law are identified and recommendations are made especially with regard to the alternative measures by which children can testify. Guidelines are also suggested for admissible cross-examination. New sentencing options are recommended and possible aggravating circumstances which ought to play a role during the consideration of a suitable and just sentence for sexual crimes with children are suggested.Criminal and Procedural LawLL.D

Chaperone-based procedure to increase yields of soluble recombinant proteins produced in E. coli

<p>Abstract</p> <p>Background</p> <p>The overproduction of recombinant proteins in host cells often leads to their misfolding and aggregation. Previous attempts to increase the solubility of recombinant proteins by co-overproduction of individual chaperones were only partially successful. We now assessed the effects of combined overproduction of the functionally cooperating chaperone network of the <it>E. coli </it>cytosol on the solubility of recombinant proteins.</p> <p>Results</p> <p>A two-step procedure was found to show the strongest enhancement of solubility. In a first step, the four chaperone systems GroEL/GroES, DnaK/DnaJ/GrpE, ClpB and the small HSPs IbpA/IbpB, were coordinately co-overproduced with recombinant proteins to optimize <it>de novo </it>folding. In a second step, protein biosynthesis was inhibited to permit chaperone mediated refolding of misfolded and aggregated proteins <it>in vivo</it>. This novel strategy increased the solubility of 70% of 64 different heterologous proteins tested up to 42-fold.</p> <p>Conclusion</p> <p>The engineered <it>E. coli </it>strains and the two-step procedure presented here led to a remarkable increase in the solubility of a various recombinant proteins and should be applicable to a wide range of target proteins produced in biotechnology.</p