The UBA domain of conjugating enzyme Ubc1/Ube2K facilitates assembly of K48/K63‐branched ubiquitin chains

The assembly of a specific polymeric ubiquitin chain on a target protein is a key event in the regulation of numerous cellular processes. Yet, the mechanisms that govern the selective synthesis of particular polyubiquitin signals remain enigmatic. The homologous ubiquitin‐conjugating (E2) enzymes Ubc1 (budding yeast) and Ube2K (mammals) exclusively generate polyubiquitin linked through lysine 48 (K48). Uniquely among E2 enzymes, Ubc1 and Ube2K harbor a ubiquitin‐binding UBA domain with unknown function. We found that this UBA domain preferentially interacts with ubiquitin chains linked through lysine 63 (K63). Based on structural modeling, in vitro ubiquitination experiments, and NMR studies, we propose that the UBA domain aligns Ubc1 with K63‐linked polyubiquitin and facilitates the selective assembly of K48/K63‐branched ubiquitin conjugates. Genetic and proteomics experiments link the activity of the UBA domain, and hence the formation of this unusual ubiquitin chain topology, to the maintenance of cellular proteostasis

Recombinant bovine uteroglobin at 1.6 Å resolution: a preliminary X-ray crystallographic analysis

The crystallization of recombinant bovine uteroglobin

Ubiquitin binding by a CUE domain regulates ubiquitin chain formation by ERAD E3 ligases

Ubiquitin-binding domains (UBDs) differentially recognize ubiquitin (ub) modifications. Some of them specifically bind mono-ub, as has been shown for the CUE domain. Interestingly, so far no significant ubiquitin binding has been observed for the CUE domain of yeast Cue1p. Cue1p is receptor and activator of the ubiquitin-conjugating enzyme Ubc7p. It integrates Ubc7p into endoplasmic reticulum (ER) membrane-bound ubiquitin ligase complexes, and thus, it is crucial for ER-associated protein degradation (ERAD). Here we show that the CUE domain of Cue1p binds ubiquitin chains, which is pivotal for the efficient formation of K48-linked polyubiquitin chains in vitro. Mutations that abolish ubiquitin binding by Cue1p affect the turnover of ERAD substrates in vivo. Our data strongly imply that the CUE domain facilitates substrate ubiquitylation by stabilizing growing ubiquitin chains at the ERAD ubiquitin ligases. Hence, we demonstrate an unexpected function of a UBD in the regulation of ubiquitin chain synthesis

Test von C/SiC-Faserkeramik-Hitzeschutzmaterialproben waehrend eines realen Wiedereintritts auf FOTON Endbericht

The DLR Stuttgart manufactured two flat disk-like samples of non-ablative heat protection material. These were integrated into the ablative heat protection system of FOTON-8 by KB FOTON. After the mission and re-entry of the capsule the samples, which were positioned near the stagnation point of the capsule and thus exposed to the maximum heat load, were deintegrated and analyzed afterwards. There could be seen no damages or essential changes of the samples. Thus the German material was successfully exposed to a real re-entry for the first time. We want to point out that the material remained absolutely stable at the contact area to the ablative Russian material. This proves the compatibility between the different materials and demonstrates that the integration of the ceramic tile to the nose of the EXPRESS capsule should be possible and not too risky as it is actually planned. (orig.)Es wurden zwei scheibenfoermige Probenstuecke aus nicht-ablativem Hitzeschutzmaterial aus C/SiC-Faserkeramik hergestellt und von KB FOTON in den ablativen Hitzeschutz der FOTON-8-Kapsel integriert. Nach dem Flug und Wiedereintritt der Kapsel wurden die Proben, die nahe des Staupunktes der maximalen Last ausgesetzt waren, deintegriert und anschliessend analysiert. Es konnten keine wesentlichen Schaedigungen oder Veraenderungen festgestellt werden. Damit wurde erstmalig dieses Material erfolgreich einem realen Wiedereintritt ausgesetzt, wobei hervorzuheben ist, dass das Material auch an der Kontaktstelle zum ablativen, russischen Hitzeschutzmaterial voellig stabil geblieben ist. Dies zeigt, dass die Kompatibilitaet zwischen dem russischen und dem deutschen Material gegeben ist, und dass die Integration der Faserkeramikkachel im Staupunkt der EXPRESS-Kapsel wie geplant moeglich sein und kein zu hohes Risiko in sich bergen sollte. (orig.)SIGLEAvailable from TIB Hannover: F95B557+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany); Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA) GmbH, Bonn (Germany)DEGerman