Gene Ontology annotation through association of InterPro records with GO terms
Annotation inferences using phylogenetic trees
Electronic Gene Ontology annotations created by transferring manual GO annotations between related proteins based on shared sequence features
Combined Automated Annotation using Multiple IEA Methods
Crystal structure of SecB from Escherichia coli.
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SecB forms a homotetramer (dimer of dimers) as shown by X-ray crystallography at 2.35 angstrom resolution.
"The chaperone SecB from Escherichia coli is primarily involved in passing precursor proteins into the Sec system via specific interactions with SecA. The crystal structure of SecB from E. coli has been solved to 2.35 A resolution."
Interaction network containing conserved and essential protein complexes in Escherichia coli.
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Large-scale affinity purification/mass spectrometry identified SecB interactions with CpxR and SecA.
"A total of 857 proteins, including 198 of the most highly conserved, soluble non-ribosomal proteins essential in at least one bacterial species, were tagged successfully, whereas 648 could be purified to homogeneity and their interacting protein partners identified by mass spectrometry."
Asymmetric binding between SecA and SecB two symmetric proteins: implications for function in export.
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SecB C-terminal alpha-helices bind in the interfacial region of the SecA dimer, and this asymmetric binding facilitates conformational changes for precursor transfer.
"unexpectedly, the binding between the two symmetric molecules is asymmetric and that the C-terminal alpha-helices of SecB bind in the interfacial region of the SecA dimer."
Defining the role of the Escherichia coli chaperone SecB using comparative proteomics.
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Comparative proteomics identified the full set of SecB substrates including DegP, FhuA, FkpA, GBP, LamB, MalE, OmpA, OmpF, OmpT, OmpX, OppA, PhoE, TolB, TolC, YbgF, YcgK, YgiW and YncE.
"The SecB/A dependence of 12 secretory proteins affected by the secB null mutation (DegP, FhuA, FkpA, OmpT, OmpX, OppA, TolB, TolC, YbgF, YcgK, YgiW, and YncE) was confirmed by "classical" pulse-labeling experiments. Our study more than triples the number of known SecB-dependent secretory proteins and shows that the primary role of SecB is to facilitate the targeting of secretory proteins to the Sec-translocase."
Sites of interaction of a precursor polypeptide on the export chaperone SecB mapped by site-directed spin labeling.
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Site-directed spin labeling and EPR mapped the binding sites of unfolded precursor galactose-binding protein on SecB surface, showing contact with a large portion of the small chaperone surface. A model for transfer of the ligand from SecB to SecA was proposed.
"Capture of the precursor polypeptides before they fold is achieved by the promiscuous binding to the chaperone SecB. SecB delivers its ligand to export sites through its specific binding to SecA"
Direct observation of chaperone-induced changes in a protein folding pathway.
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Single-molecule optical tweezers and MD simulations showed SecB completely prevents stable tertiary contacts in MBP, retaining it in a molten-globule-like state.
"Interactions with SecB completely prevent stable tertiary contacts in the core structure but have no detectable effect on the folding of the external alpha helices."
Protein abundance profiling of the Escherichia coli cytosol.
Global functional atlas of Escherichia coli encompassing previously uncharacterized proteins.
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Large-scale functional atlas showing SecB-CpxR interaction.
"we performed an extensive proteomic survey using affinity-tagged E. coli strains and generated comprehensive genomic context inferences to derive a high-confidence compendium for virtually the entire proteome consisting of 5,993 putative physical interactions"
Orientation of SecA and SecB in complex, derived from disulfide cross-linking.
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Disulfide cross-linking defined the relative orientation of SecA and SecB within the complex. Two SecA protomers bind one SecB tetramer.
"The tetrameric cytoplasmic chaperone SecB binds to precursors of exported proteins before they can become stably folded and delivers them to SecA."
The binding cascade of SecB to SecA to SecY/E mediates preprotein targeting to the E. coli plasma membrane.
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SecB has a dual function in stabilizing precursors and delivering them to membrane-bound SecA. The SecB-SecA-SecYEG binding cascade was characterized with binding affinities.
"SecB has a dual function in stabilizing the precursor and in passing it on to membrane-bound SecA, the next step in the pathway."
Cytosolic factor purified from Escherichia coli is necessary and sufficient for the export of a preprotein and is a homotetramer of SecB.
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SecB purified as a 64-kDa homotetramer of identical 16-kDa subunits from the cytosol. It is necessary and sufficient for translocation of preproteins into inverted membrane vesicles.
"The purified factor amounts to 0.08% of the cytosolic proteins and is a 64-kDa tetramer consisting of four identical 16-kDa subunits."
Escherichia coli SecB protein associates with exported protein precursors in vivo.
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SecB associates with precursor forms of exported proteins (MBP, LamB, OmpA) in vivo. The SecB-precursor complex is short-lived, consistent with an export intermediate.
"in wild-type growing cells, SecB protein associates with precursor forms of exported proteins, such as the periplasmic maltose-binding protein (MBP) and the outer-membrane proteins LamB and OmpA."
Structural basis for the antifolding activity of a molecular chaperone.
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NMR structures of SecB in complex with substrates showed that precursor proteins wrap around the SecB homotetramer, providing the structural basis for antifolding activity.
"The most remarkable feature is that PhoA wraps around SecB in an overall arrangement that maximizes the interacting surface between the client protein, which is held in an unfolded conformation, and the chaperone."
The antifolding activity of SecB promotes the export of the E. coli maltose-binding protein.
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SecB prevents premature folding of newly synthesized MBP precursor, promoting export. The antifolding activity was demonstrated by genetic suppression and in vitro folding assays.
"The antifolding activity of SecB was demonstrated by the following: the defect in MBP export in SecB- cells was suppressed by mutational alterations affecting MBP folding"
Purified secB protein of Escherichia coli retards folding and promotes membrane translocation of the maltose-binding protein in vitro.
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Purified SecB retards folding of precursor MBP and promotes its translocation into inverted membrane vesicles in vitro. SecB is a soluble, cytoplasmic, multimeric protein of identical 17-kDa subunits.
"The purified protein also quantitatively retarded folding of precursor MBP into a stable, protease-resistant conformation in the absence of membranes."
Mutations in a new gene, secB, cause defective protein localization in Escherichia coli.
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SecB was identified as a new gene required for protein secretion. secB mutants showed defective localization of MBP and OmpF. The secB product was proposed as a component of the E. coli secretory apparatus.
"These secB mutants were defective in the localization of maltose-binding protein and, in at least one case, OmpF protein."
The molecular chaperone SecB is released from the carboxy-terminus of SecA during initiation of precursor protein translocation.
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The SecB-binding site on SecA is confined to the extreme C-terminal 22 amino acids. SecB is released from SecA upon ATP binding, at the onset of translocation.
"The chaperone SecB keeps precursor proteins in a translocation-competent state and targets them to SecA at the translocation sites in the cytoplasmic membrane of Escherichia coli."
Deep research synthesis for Escherichia coli SecB
Unfolded Protein Binding Annotation Review
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GO:0051082 is obsolete, and SecB is a carrier-holdase for which GO:0140309 is appropriate.
"GO:0051082 is now formally obsolete"