Abstract
In the bacterial cytosol, degradation of ssrA-tagged proteins is primarily carried out by the proteolytic machine ClpXP in a process which is stimulated by a ClpX-specific adaptor protein, SspB. Here we elucidate the steps required for binding and transfer of ssrA-tagged substrates from SspB to ClpX. The N-terminal region of SspB is essential for its interaction with ssrA-tagged substrates, while a short conserved region at the C terminus of SspB interacts specifically with the N domain of ClpX. A single point mutation within the conserved C-terminal region of SspB is sufficient to abolish the SspB-mediated degradation of ssrA-tagged proteins by ClpXP. We propose that this region represents a common motif for the recognition of ClpX as the C-terminal region of SspB shares considerable homology with the other ClpX-specific adaptor protein, RssB. Through docking of SspB to the N-terminal domain of ClpX, the substrate is delivered to the substrate binding site in ClpX.
MeSH terms
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ATPases Associated with Diverse Cellular Activities
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Adaptor Proteins, Vesicular Transport / metabolism
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Adenosine Triphosphatases / metabolism*
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Adenosine Triphosphate / metabolism
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Adhesins, Bacterial / metabolism
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Adhesins, Bacterial / physiology*
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Amino Acid Motifs
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Amino Acid Sequence
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Bacterial Physiological Phenomena
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Bacterial Proteins / chemistry
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Endopeptidase Clp
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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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Models, Biological
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Molecular Chaperones
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Molecular Sequence Data
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Multigene Family
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Peptides / chemistry
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Plasmids / metabolism
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Protein Binding
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Protein Structure, Secondary
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Protein Structure, Tertiary
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RNA, Bacterial / chemistry
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RNA, Bacterial / metabolism*
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Sequence Homology, Amino Acid
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Spectrophotometry
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Time Factors
Substances
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Adaptor Proteins, Vesicular Transport
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Adhesins, Bacterial
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Bacterial Proteins
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Escherichia coli Proteins
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Luminescent Proteins
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Molecular Chaperones
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Peptides
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RNA, Bacterial
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tmRNA
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salivary agglutinin receptor, Streptocococcus
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Green Fluorescent Proteins
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Adenosine Triphosphate
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Endopeptidase Clp
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Adenosine Triphosphatases
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ClpX protein, E coli
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ATPases Associated with Diverse Cellular Activities