Characterisation of the passive permeability barrier of nuclear pore complexes

Nuclear pore complexes (NPCs) restrict uncontrolled nucleocytoplasmic fluxes of inert macromolecules but permit facilitated translocation of nuclear transport receptors and their cargo complexes. We probed the passive barrier of NPCs and observed sieve-like properties with a dominating mesh or channel radius of 2.6 nm, which is narrower than proposed earlier. A small fraction of diffusion channels has a wider opening, explaining the very slow passage of larger molecules. The observed dominant passive diameter approximates the distance of adjacent hydrophobic clusters of FG repeats, supporting the model that the barrier is made of FG repeat domains cross-linked with a spacing of an FG repeat unit length. Wheat germ agglutinin and the dominant-negative importin β45-462 fragment were previously regarded as selective inhibitors of facilitated NPC passage. We now observed that they do not distinguish between the passive and the facilitated mode. Instead, their inhibitory effect correlates with the size of the NPC-passing molecule. They have little effect on small species, inhibit the passage of green fluorescent protein-sized objects >10-fold and virtually block the translocation of larger ones. This suggests that passive and facilitated NPC passage proceed through one and the same permeability barrier

The putative RNase P motif in the DEAD box helicase Hera is dispensable for efficient interaction with RNA and helicase activity

DEAD box helicases use the energy of ATP hydrolysis to remodel RNA structures or RNA/protein complexes. They share a common helicase core with conserved signature motifs, and additional domains may confer substrate specificity. Identification of a specific substrate is crucial towards understanding the physiological role of a helicase. RNA binding and ATPase stimulation are necessary, but not sufficient criteria for a bona fide helicase substrate. Here, we report single molecule FRET experiments that identify fragments of the 23S rRNA comprising hairpin 92 and RNase P RNA as substrates for the Thermus thermophilus DEAD box helicase Hera. Both substrates induce a switch to the closed conformation of the helicase core and stimulate the intrinsic ATPase activity of Hera. Binding of these RNAs is mediated by the Hera C-terminal domain, but does not require a previously proposed putative RNase P motif within this domain. ATP-dependent unwinding of a short helix adjacent to hairpin 92 in the ribosomal RNA suggests a specific role for Hera in ribosome assembly, analogously to the Escherichia coli and Bacillus subtilis helicases DbpA and YxiN. In addition, the specificity of Hera for RNase P RNA may be required for RNase P RNA folding or RNase P assembly

3_04_Bedeutung-Konzeptorientierung

Ergebnisse empirischer Studien zeigen die Wirksamkeit von Konzeptorientierung im Fachunterricht

3_11_Reflexion-Konzeptorientierung

Reflexion: Konzeptorientierung in einem Fachunterricht mit digitalen Medien

2_09_Arbeitsauftrag

Arbeitsauftrag 1. &2. Stunde. Gegliedert in Arbeitsauftrag heute und Arbeitsauftrag bis zum nächsten Klausurtag

2_03_Leitlinien

Die Präsentation stellt bildungspolitische Dokumente vor, die entwickelt wurden um die Digitalisierung an Schulen in Deutschland voranzutreiben. Unter anderem definiert das bildungspolitische Dokument „Kompetenzen in einer digitalen Welt“ (KMK, 2017) Kompetenzen, die Schülerinnen und Schüler in einer digitalen Welt beherrschen sollen und stellt den Rahmen für den Digitalisierungsprozess an Schulen in Deutschland dar

2_10_Abschluss

Unterricht mit digitalen Medien – Wie geht es weiter? Zusammenfassung, offene Fragen, Ausblic

3_03_Einfuehrung-Konzeptorientierung

Es gibt bildungspolitische und pädagogisch-psychologische Gründe Unterricht an (Basis-)Konzepten auszurichten

4_02_Einführung-kognitive-Aktivierung

Kognitive Aktivierung kann zu einem tieferen Verständnis der Inhalte und damit besserer Behaltensleistung führen

4_03_Bedeutung-kognitive-Aktivierung

Ergebnisse empirischer Studien zeigen die Wirksamkeit von kognitiver Aktivierung im Fachunterricht