title: Targeted delivery of an ssrA-tagged substrate by the adaptor protein SspB to its cognate AAA+ protein ClpX.
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.
authors.affiliation: Zentrum für Molekulare Biologie Heidelberg, Universität Heidelberg, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany. d.dougan@zmbh.uni-heidelberg.de
authors.forename: David A
authors.initials: DA
authors.lastname: Dougan
authors.forename: Eilika
authors.initials: E
authors.lastname: Weber-Ban
authors.forename: Bernd
authors.initials: B
authors.lastname: Bukau
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D018829:Adhesins, Bacterial / Q000378:metabolism / Q000502:physiology*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D018407:Bacterial Physiological Phenomena; D001426:Bacterial Proteins / Q000737:chemistry; D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008954:Models, Biological; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D005810:Multigene Family; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012329:RNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry; D013997:Time Factors
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008164:Luminescent Proteins; D018832:Molecular Chaperones; D010455:Peptides; D012329:RNA, Bacterial; C096222:tmRNA; C068465:salivary agglutinin receptor, Streptocococcus; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities