scholarly journals Formyl-methionine as an N-degron of a eukaryotic N-end rule pathway

Science ◽  
2018 ◽  
Vol 362 (6418) ◽  
pp. eaat0174 ◽  
Author(s):  
Jeong-Mok Kim ◽  
Ok-Hee Seok ◽  
Shinyeong Ju ◽  
Ji-Eun Heo ◽  
Jeonghun Yeom ◽  
...  
Keyword(s):  
Amino Acids ◽  
Stationary Phase ◽  
Ubiquitin Ligase ◽  
Bacterial Proteins ◽  
Cytosolic Ribosomes

In bacteria, nascent proteins bear the pretranslationally generated N-terminal (Nt) formyl-methionine (fMet) residue. Nt-fMet of bacterial proteins is a degradation signal, termed fMet/N-degron. By contrast, proteins synthesized by cytosolic ribosomes of eukaryotes were presumed to bear unformylated Nt-Met. Here we found that the yeast formyltransferase Fmt1, although imported into mitochondria, could also produce Nt-formylated proteins in the cytosol. Nt-formylated proteins were strongly up-regulated in stationary phase or upon starvation for specific amino acids. This up-regulation strictly required the Gcn2 kinase, which phosphorylates Fmt1 and mediates its retention in the cytosol. We also found that the Nt-fMet residues of Nt-formylated proteins act as fMet/N-degrons and identified the Psh1 ubiquitin ligase as the recognition component of the eukaryotic fMet/N-end rule pathway, which destroys Nt-formylated proteins.

scholarly journals The El Tor Biotype of Vibrio cholerae Exhibits a Growth Advantage in the Stationary Phase in Mixed Cultures with the Classical Biotype

2009 ◽  
Vol 192 (4) ◽  
pp. 955-963 ◽  
Author(s):  
Subhra Pradhan ◽  
Amit K. Baidya ◽  
Amalendu Ghosh ◽  
Kalidas Paul ◽  
Rukhsana Chowdhury
Keyword(s):  
Amino Acids ◽  
Stationary Phase ◽  
Vibrio Cholerae ◽  
Competitive Growth ◽  
Small Peptides ◽  
Ileal Loop ◽  
Infant Mouse ◽  
Culture Filtrates ◽  
El Tor

ABSTRACT Vibrio cholerae strains of the O1 serogroup that typically cause epidemic cholera can be classified into two biotypes, classical and El Tor. The El Tor biotype emerged in 1961 and subsequently displaced the classical biotype as a cause of cholera throughout the world. In this study we demonstrate that when strains of the El Tor and classical biotypes were cocultured in standard LB medium, the El Tor strains clearly had a competitive growth advantage over the classical biotype starting from the late stationary phase and could eventually take over the population. The classical biotype produces extracellular protease(s) in the stationary phase, and the amounts of amino acids and small peptides in the late stationary and death phase culture filtrates of the classical biotype were higher than those in the corresponding culture filtrates of the El Tor biotype. The El Tor biotype cells could utilize the amino acids more efficiently than the classical biotype under the alkaline pH of the stationary phase cultures but not in medium buffered to neutral pH. The growth advantage of the El Tor biotype was also observed in vivo using the ligated rabbit ileal loop and infant mouse animal models.

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