ABSTRACT
Translation of consecutive proline motifs causes ribosome stalling and requires rescue via the action of a specific translation elongation factor, EF-P in bacteria and archaeal/eukaryotic a/eIF5A. In Eukarya, Archaea, and all bacteria investigated so far, the functionality of this translation elongation factor depends on specific and rather unusual post-translational modifications. The phylum Actinobacteria, which includes the genera Corynebacterium, Mycobacterium, and Streptomyces, is of both medical and economic significance. Here, we report that EF-P is required in these bacteria in particular for the translation of proteins involved in amino acid and secondary metabolite production. Notably, EF-P of Actinobacteria species does not need any post-translational modification for activation. While the function and overall 3D structure of this EF-P type is conserved, the loop containing the conserved lysine is flanked by two essential prolines that rigidify it. Actinobacteria's EF-P represents a unique subfamily that works without any modification.
Subject(s)
Actinobacteria/metabolism , Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Peptide Elongation Factors/chemistry , Peptide Elongation Factors/metabolism , Amino Acid Motifs , Amino Acid Sequence , Amino Acids/metabolism , Conserved Sequence , Crystallography, X-Ray , Models, Molecular , Phylogeny , Protein Processing, Post-Translational , Proteomics , Structure-Activity RelationshipABSTRACT
Recent experimental investigations on the reduction of internal quantum efficiency with increasing current density in (AlInGa)N quantum well structures show that Auger recombination is a significant contributor to the so-called "droop" phenomenon. Using photoluminescence (PL) test structures, we find Auger processes are responsible for at least 15 % of the measured efficiency droop. Furthermore, we confirm that electron-electron-hole (nnp) is stronger than electron-hole-hole (npp) Auger recombination in standard LEDs. The ratio of respective Auger coefficients is determined to be in the range 1 < Cnnp/Cnpp ≤ 12. This asymmetry is shown to limit the detection efficiency of Auger processes in our PL-based approach.
ABSTRACT
Prospective negative cognitions are suggested to play an important role in maintaining anxiety disorders and major depressive disorder (MDD). However, little is known about positive prospective mental imagery. This study investigated differences in prospective mental imagery among 27 patients with anxiety disorders, 24 patients with MDD, and 32 control participants. Measures of both deliberately generated and intrusive imagery were completed. Results indicated that both patients with anxiety disorders and those with MDD provided poorer vividness ratings for deliberately generated prospective positive scenarios compared to the control group. Patients with anxiety disorders showed a greater ability to vividly generate imagery for prospective negative scenarios than both patients with MDD and control participants. Finally, both clinical groups reported greater levels of intrusive prospective imagery of personally-relevant events as compared to the control group. The current findings underline the necessity to target prospective positive mental imagery in treating MDD and anxiety disorders.
