Protein Synthesis and Degradation
Unfolding or aggregation, that is the questionCellular processes accompanying protein aggregation are diverse and entangled, making it difficult to investigate the underlying molecular processes in a time-resolved way. Gottlieb, Thompson, and colleagues address this shortcoming using a chemical biology approach to monitor ubiquitination within the first 10 min after the initiation of protein aggregation. Intriguingly, unfolding rather than aggregation seems to trigger the observed events. This work might provide a method to answer open questions regarding the regulation of the proteostasis network upon protein misfolding.
Depupylase Dop Requires Inorganic Phosphate in the Active Site for CatalysisAnalogous to eukaryotic ubiquitination, proteins in actinobacteria can be post-translationally modified in a process referred to as pupylation, the covalent attachment of prokaryotic ubiquitin-like protein Pup to lysine side chains of the target protein via an isopeptide bond. As in eukaryotes, an opposing activity counteracts the modification by specific cleavage of the isopeptide bond formed with Pup. However, the enzymes involved in pupylation and depupylation have evolved independently of ubiquitination and are related to the family of ATP-binding and hydrolyzing carboxylate-amine ligases of the glutamine synthetase type.