Affiliation:
1. Department of Chemistry, Brown University, Providence, Rhode Island, USA
Abstract
ABSTRACT
Pupylation is a posttranslational modification peculiar to actinobacteria wherein proteins are covalently modified with a small protein called the prokaryotic ubiquitin-like protein (Pup). Like ubiquitination in eukaryotes, this phenomenon has been associated with proteasome-mediated protein degradation in mycobacteria. Here, we report studies of pupylation in a streptomycete that is phylogentically related to mycobacteria. We constructed mutants of
Streptomyces coelicolor
lacking PafA (Pup ligase), the proteasome, and the Pup-proteasome system. We found that these mutants share a high susceptibility to oxidative stress compared to that of the wild-type strain. Remarkably, we found that the
pafA
null mutant has a sporulation defect not seen in strains lacking the Pup-proteasome system. In proteomics experiments facilitated by an affinity-tagged variant of Pup, we identified 110 pupylated proteins in
S. coelicolor
strains having and lacking genes encoding the 20S proteasome. Our findings shed new light on this unusual posttranslational modification and its role in
Streptomyces
physiology.
IMPORTANCE
The presence of 20S proteasomes reminiscent of those in eukaryotes and a functional equivalent of ubiquitin, known as the prokaryotic ubiquitin-like protein (Pup), in actinobacteria have motivated reevaluations of protein homeostasis in prokaryotes. Though the Pup-proteasome system has been studied extensively in mycobacteria, it is much less understood in streptomycetes, members of a large genus of actinobacteria known for highly choreographed life cycles in which phases of morphological differentiation, sporulation, and secondary metabolism are often regulated by protein metabolism. Here, we define constituents of the pupylome in
Streptomyces coelicolor
for the first time and present new evidence that links pupylation and the oxidative stress response in this bacterium. Surprisingly, we found that the Pup ligase has a Pup-independent role in sporulation.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
33 articles.
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