Abstract
The bacterial L9 (bL9) protein expressed and purified from Escherichia coli is stably phosphorylated. We mapped seven Ser/Thr phosphorylation sites, all of which but one are located at the carboxyl-terminal domain (CTD). When a histidine tag is fused to the C-terminus, bL9 is no longer phosphorylated. Phosphorylation of bL9 causes complete disordering of its CTD and helps cell survival under nutrient-limiting conditions. Previous structural studies of the ribosome have shown that bL9 exhibits two distinct conformations, one of which competes with binding of RelA to the 30s rRNA and prevents RelA activation. Taken together, we suggest that the flexibility of the bL9 CTD enabled by phosphorylation would remove the steric hindrance, serving as a previously unknown mechanism to regulate RelA function and help cell survival under starvation stress.
Keywords:
bacterial L9; phosphorylation; starvation stress.
© 2017 Federation of European Biochemical Societies.
MeSH terms
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Amino Acid Sequence
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Bacterial Proteins / chemistry*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Binding Sites
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Cloning, Molecular
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Crystallography, X-Ray
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Culture Media / pharmacology
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Escherichia coli / drug effects
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Escherichia coli / genetics
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Escherichia coli / metabolism*
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Gene Expression
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Geobacillus stearothermophilus / chemistry*
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Geobacillus stearothermophilus / metabolism
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Models, Molecular
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Mutation
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Phosphorylation
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Protein Binding
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Protein Conformation, alpha-Helical
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Protein Conformation, beta-Strand
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Protein Interaction Domains and Motifs
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Protein Structure, Tertiary
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Ribosomal Proteins / chemistry*
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Ribosomal Proteins / genetics
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Ribosomal Proteins / metabolism
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Ribosomes / chemistry*
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Ribosomes / genetics
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Ribosomes / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
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Stress, Physiological*
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Substrate Specificity
Substances
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Bacterial Proteins
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Culture Media
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Recombinant Proteins
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Ribosomal Proteins
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ribosomal protein L9