Specialized Listeria monocytogenes produce tailocins to provide a population-level competitive growth advantage.

Tailocins are phage tail-like bacteriocins produced by various bacterial species to kill kin competitors. Given that tailocin release is dependent upon cell lysis, regulation of tailocin production at the single-cell and population level remains unclear. Here we used flow cytometry, competition assays and structural characterization of tailocin production in a human bacterial pathogen, Listeria monocytogenes.

The prokaryotic ubiquitin-like protein presents poor cleavage sites for proteasomal degradation.

In an event reminiscent of eukaryotic ubiquitination, the bacterial prokaryotic ubiquitin-like protein (Pup)-proteasome system (PPS) marks target proteins for proteasomal degradation by covalently attaching Pup, the bacterial tagging molecule. Yet, ubiquitin is released from its conjugated target following proteasome binding, whereas Pup enters the proteasome and remains conjugated to the target. Here, we report that although Pup can be degraded by the bacterial proteasome, it lacks favorable 20S core particle (CP) cleavage sites and is thus a very poor 20S CP substrate.

Multiple layers of regulation determine the cellular levels of the Pup ligase PafA in Mycobacterium smegmatis.

Despite being a destructive process, regulated protein degradation is fundamental for proper cell function. While regulated proteolysis in eukaryotes largely involves the ubiquitin-proteasome system (UPS), most bacterial species rely on multiple ATP-dependent proteases, such as the Clp proteases. Mycobacteria and related actinobacterial species also possess a degradation system analogous in its function to the UPS.

How to control an intracellular proteolytic system: Coordinated regulatory switches in the mycobacterial Pup-proteasome system.

Intracellular proteolysis is critical for the proper functioning of all cells, owing to its involvement in a wide range of processes. Because of the destructive nature of protein degradation, intracellular proteolysis is restricted by control mechanisms at almost every step of the proteolytic process. Understanding the coordination of such mechanisms is a challenging task, especially in systems as complex as the eukaryotic ubiquitin-proteasome system (UPS).

The regulatory significance of tag recycling in the mycobacterial Pup-proteasome system.

Pup, a ubiquitin analog, tags proteins for degradation by the bacterial proteasome. As an intracellular proteolytic system, the Pup-proteasome system (PPS) must be carefully regulated to prevent excessive protein degradation. Currently, those factors underlying PPS regulation remain poorly understood.