Abstract
Events that stall bacterial protein synthesis activate the ssrA-tagging machinery, resulting in resumption of translation and addition of an 11-residue peptide to the carboxyl terminus of the nascent chain. This ssrA-encoded peptide tag marks the incomplete protein for degradation by the energy-dependent ClpXP protease. Here, a ribosome-associated protein, SspB, was found to bind specifically to ssrA-tagged proteins and to enhance recognition of these proteins by ClpXP. Cells with an sspB mutation are defective in degrading ssrA-tagged proteins, demonstrating that SspB is a specificity-enhancing factor for ClpXP that controls substrate choice.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenosine Triphosphatases / metabolism*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism*
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Endopeptidase Clp
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Escherichia coli / enzymology
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Escherichia coli / metabolism*
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Escherichia coli Proteins*
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Green Fluorescent Proteins
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Luminescent Proteins / metabolism
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Mutation
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Oligopeptides / chemistry
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Oligopeptides / genetics
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Oligopeptides / metabolism*
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Operon
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Ribosomes / metabolism
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Serine Endopeptidases / metabolism*
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Substrate Specificity
Substances
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Bacterial Proteins
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Escherichia coli Proteins
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Luminescent Proteins
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Oligopeptides
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SspA protein, E coli
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Green Fluorescent Proteins
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Serine Endopeptidases
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ClpXP protease, E coli
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Endopeptidase Clp
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Adenosine Triphosphatases