Calcium binding to a remote site can replace magnesium as cofactor for mitochondrial Hsp90 (TRAP1) ATPase activity.

The Hsp90 molecular chaperones are ATP-dependent enzymes that maintain protein homeostasis and regulate many essential cellular processes. Higher eukaryotes have organelle-specific Hsp90 paralogs that are adapted to each subcellular environment. The mitochondrial Hsp90, TNF receptor-associated protein 1 (TRAP1), supports the folding and activity of electron transport components and is increasingly appreciated as a critical player in mitochondrial signaling. Calcium plays a well-known and important regulatory role in mitochondria where it can accumulate to much higher concentrations than in the cytoplasm. Surprisingly, we found here that calcium can replace magnesium, the essential enzymatic cofactor, to support TRAP1 ATPase activity. Anomalous X-ray diffraction experiments revealed a calcium-binding site within the TRAP1 nucleotide-binding pocket located near the ATP α-phosphate and completely distinct from the magnesium-binding site adjacent to the β- and γ-phosphates. In the presence of magnesium, ATP hydrolysis by TRAP1, as with other Hsp90s, was noncooperative, whereas calcium binding resulted in cooperative hydrolysis by the two protomers within the Hsp90 dimer. The structural data suggested a mechanism for this cooperative behavior. Because of the cooperativity, at high ATP concentrations, ATPase activity was higher with calcium, whereas the converse was observed at low ATP concentrations. Integrating these observations, we propose a model in which the divalent cation choice can control switching between noncooperative and cooperative TRAP1 ATPase mechanisms in response to varying ATP concentrations. This switching may facilitate coordination between cellular energetics, mitochondrial signaling, and protein homeostasis via alterations in the TRAP1 ATP-driven cycle and its consequent effects on different mitochondrial clients

Jim Agard: A Retrospective

The subject of illusion has been at the core of Jim’s work from the get-go. So when he serendipitously met some guy one night who was toying with a bent hanger, insisting Jim entertain him by seeing if he could visually make the wire cube turn inside out, Jim was captivated. Moving from side to side, as instructed, Jim experienced the cube floating on an invisible axis. He went rampant. Up until then, his work had implied illusion rather than created actual illusion. A chance encounter and his discovery of the Necker cube propelled him into what would become the basis of his life’s work. Like when one learns to open one’s eyes underwater for the first time, everything becomes wildly different, just knowing there is a whole other way of seeing. Jim’s work is purely non-objective and formal, yet equally laden with profound conceptual significance. It invites an approach that is lucid and straightforward, while encouraging a willingness to let the focus blur. To hold these views simultaneously. To see and then hyper-see and be willing to not see, and in not seeing, see even more. [excerpt]https://cupola.gettysburg.edu/artcatalogs/1003/thumbnail.jp

Unfolding simulations reveal the mechanism of extreme unfolding cooperativity in the kinetically stable alpha-lytic protease.

Kinetically stable proteins, those whose stability is derived from their slow unfolding kinetics and not thermodynamics, are examples of evolution's best attempts at suppressing unfolding. Especially in highly proteolytic environments, both partially and fully unfolded proteins face potential inactivation through degradation and/or aggregation, hence, slowing unfolding can greatly extend a protein's functional lifetime. The prokaryotic serine protease alpha-lytic protease (alphaLP) has done just that, as its unfolding is both very slow (t(1/2) approximately 1 year) and so cooperative that partial unfolding is negligible, providing a functional advantage over its thermodynamically stable homologs, such as trypsin. Previous studies have identified regions of the domain interface as critical to alphaLP unfolding, though a complete description of the unfolding pathway is missing. In order to identify the alphaLP unfolding pathway and the mechanism for its extreme cooperativity, we performed high temperature molecular dynamics unfolding simulations of both alphaLP and trypsin. The simulated alphaLP unfolding pathway produces a robust transition state ensemble consistent with prior biochemical experiments and clearly shows that unfolding proceeds through a preferential disruption of the domain interface. Through a novel method of calculating unfolding cooperativity, we show that alphaLP unfolds extremely cooperatively while trypsin unfolds gradually. Finally, by examining the behavior of both domain interfaces, we propose a model for the differential unfolding cooperativity of alphaLP and trypsin involving three key regions that differ between the kinetically stable and thermodynamically stable classes of serine proteases

Les Studien über die Deutschen : un correctif à la théorie du processus de civilisation ?

Dans les Studien über die Deutschen, Norbert Elias renvoie à son livre de 1939 sur le processus de civilisation. Mais les Studien ont un autre objet (l'histoire allemande, la ‘décivilisation‘) et ont été publiées dans un tout autre contexte. Sans remettre en cause les principes fondamentaux de sa théorie, Elias l'infléchit sur trois points : 1. Il insiste sur l'humanisation de l'autocontrôle. 2. Il met en évidence le caractère précaire de la civilisation et introduit le concept de décivilisation 3. Tout en mettant en œuvre sa sociologie des figurations, il l'adapte à la complexité du matériau historique

Dissecting apoptosis the omics way

A combined analysis of transcription, translation and protein degradation reveals the global effects of an anticancer drug on tumour cells

Telomeres cluster de novo before the initiation of synapsis: a three-dimensional spatial analysis of telomere positions before and during meiotic prophase.

We have analyzed the progressive changes in the spatial distribution of telomeres during meiosis using three-dimensional, high resolution fluorescence microscopy. Fixed meiotic cells of maize (Zea mays L.) were subjected to in situ hybridization under conditions that preserved chromosome structure, allowing identification of stage-dependent changes in telomere arrangements. We found that nuclei at the last somatic prophase before meiosis exhibit a nonrandom, polarized chromosome organization resulting in a loose grouping of telomeres. Quantitative measurements on the spatial arrangements of telomeres revealed that, as cells passed through premeiotic interphase and into leptotene, there was an increase in the frequency of large telomere-to-telomere distances and a decrease in the bias toward peripheral localization of telomeres. By leptotene, there was no obvious evidence of telomere grouping, and the large, singular nucleolus was internally located, nearly concentric with the nucleus. At the end of leptotene, telomeres clustered de novo at the nuclear periphery, coincident with a displacement of the nucleolus to one side. The telomere cluster persisted throughout zygotene and into early pachytene. The nucleolus was adjacent to the cluster at zygotene. At the pachytene stage, telomeres rearranged again by dispersing throughout the nuclear periphery. The stage-dependent changes in telomere arrangements are suggestive of specific, active telomere-associated motility processes with meiotic functions. Thus, the formation of the cluster itself is an early event in the nuclear reorganizations associated with meiosis and may reflect a control point in the initiation of synapsis or crossing over

Paper-Based Microfluidic Devices For Forensic Sciences: Development And Validation Of Innovative Tools

Laboratory analyses usually require sophisticated equipment and skilled personnel. However, very often, the use of simplified procedures and techniques in various working conditions can prove useful in solving several problems. Forensic applications represent an emblematic example of this requirement to simplify and solve various difficulties. Legal medicine requires both highly sophisticated techniques to solve analytical problems and simple techniques with fast procedures that allow analyses to be carried out outside the laboratory, in remote areas by unqualified personnel. The implementation of paper-based microfluidic analytical devices (PADs) for legal medicine presents an opportunity to tackle all the aforementioned limitations and requirements in the field of forensic science. It is also important to note that little to no sample preparation is required, with the ability to use many samples directly onto the PADs for the analysis of the desired analyte. PADs are very inexpensive to produce and ca

A Study of the Influence of the Restorative Justice Model on Out-of-School Suspensions in a Large School District

The purpose of this quantitative study was to investigate whether the Restorative Justice model influenced the number of days that students were suspended out-of-school or the number of out-of-school suspension incidents. In addition, the researcher analyzed whether the Restorative Justice model had different impacts for the subgroups of students qualifying for free and reduced lunch (FRL), English Learners (EL), students qualifying for exceptional student education services (ESE), and three ethnic subgroups (White, Black, and Hispanic) in an urban school district in Central Florida for the sixth-, seventh-, and eighth-grade students for the seven school years from 2010-2011 to 2016-2017. Primary data analysis strategies were descriptive statistics and visual analyses utilizing an interrupted time series design. The findings can be helpful in informing decision makers if the Restorative Justice model is having a positive influence on decreasing out-of-school suspension incidents and/or out-of-school suspension days

Uganda\u27s Agard Didi Views on Rwanda Conflict

Didi talks of strong anti-RPF, Tutsi, and Uganda propaganda that has brainwashed the population of Rwanda. Believes this propaganda will make the war unwinnable for the RPF.https://digitalcommons.georgefox.edu/rawson_rwanda/1197/thumbnail.jp