SecB

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005829 cytosol	IBA GO_REF:0000033	ACCEPT	Summary: SecB is a soluble, cytosolic protein. This is well-established by purification as a cytosolic factor (PMID:2649892) and proteomics profiling (PMID:18304323). The IBA annotation is consistent with multiple IDA annotations for the same term. Reason: SecB is definitively a cytosolic protein. Watanabe and Blobel purified it as a "cytosolic factor" (PMID:2649892), and it was identified in cytosolic proteomics (PMID:18304323). UniProt annotation confirms "Cytoplasm" subcellular location. The IBA annotation is fully supported. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002199630 · PANTHER:PTN002199630 SUPPORTS TRANSFER Current PTHR36918 PAINT retains GO:0005829 at this ancestral node. UniProtKB:P0AG86 · SecB SUPPORTS TRANSFER SecB itself is the descendant evidence in the exact GOA trace and has direct cytosol evidence. Supporting Evidence: PMID:2649892 We have purified to homogeneity a cytosolic factor from Escherichia coli that is required for the translocation of a preprotein into inverted vesicles of the E. coli plasma membrane. PMID:18304323 we identified 1103 proteins from the cytosolic fraction of the Escherichia coli strain MC4100
GO:0036506 maintenance of unfolded protein	IBA GO_REF:0000033	ACCEPT	Summary: SecB maintains precursor proteins in an unfolded, translocation-competent state. This antifolding/holdase activity is the core biological process of SecB, demonstrated by both in vivo and in vitro experiments (PMID:2834066, PMID:2848249, PMID:18048690). Reason: This is a core function of SecB. Collier et al. showed that SecB prevents premature folding of MBP precursor (PMID:2834066). Weiss et al. demonstrated that purified SecB "quantitatively retarded folding of precursor MBP into a stable, protease-resistant conformation" (PMID:2848249). Bechtluft et al. showed by single-molecule optical tweezers that SecB "completely prevent stable tertiary contacts" and "retains MBP in this [molten-globule] state" (PMID:18048690). The IBA annotation is well-supported by experimental evidence. Propagation Review Root cause: SOURCE STALE OR MISSING Sources checked: PANTHER:PTN002199630 · PANTHER:PTN002199630 SOURCE STALE OR MISSING Current PTHR36918 PAINT no longer serializes GO:0036506 at this node. UniProtKB:P0AG86 · SecB SOURCE STALE OR MISSING SecB is the historical descendant evidence; direct IMP and IDA rows independently establish this process. Supporting Evidence: PMID:2834066 Evidence is presented that the E. coli secB gene encodes a soluble protein that interacts with the mature region of the precursor maltose-binding protein (MBP), and promotes MBP export by preventing premature folding of the newly synthesized polypeptide into an export-incompetent form. PMID:2848249 The purified protein also quantitatively retarded folding of precursor MBP into a stable, protease-resistant conformation in the absence of membranes. PMID:18048690 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. It appears that SecB only binds to the extended or molten globulelike structure and retains MBP in this latter state.
GO:0043952 protein transport by the Sec complex	IBA GO_REF:0000033	ACCEPT	Summary: SecB is a dedicated component of the Sec-dependent protein export pathway. It delivers unfolded preproteins to SecA, which is the peripheral ATPase of the SecYEG translocon (PMID:2170023, PMID:9321390). SecB mutations cause pleiotropic defects in protein secretion (PMID:6403503). Reason: SecB is specifically dedicated to the Sec translocation pathway. The GO term comment notes this is for "proteins that compose the transport complex but not the proteins being transported." SecB is not a structural component of the translocon itself, but rather functions as the dedicated chaperone that delivers substrates to the Sec machinery. The original secB mutant was identified by defective protein secretion (PMID:6403503), and the SecB-SecA-SecYEG binding cascade is well-established (PMID:2170023). The IBA annotation is appropriate. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002199630 · PANTHER:PTN002199630 SUPPORTS TRANSFER Current PTHR36918 PAINT retains GO:0043952 at this ancestral node. UniProtKB:P0AG86 · SecB SUPPORTS TRANSFER SecB itself is the descendant evidence and has direct mutant and biochemical support for Sec-pathway transport. Supporting Evidence: PMID:2170023 The binding cascade of SecB to SecA to SecY/E mediates preprotein targeting to the E. coli plasma membrane. PMID:6403503 These secB mutants were defective in the localization of maltose-binding protein and, in at least one case, OmpF protein.
GO:0051082 unfolded protein binding	IBA GO_REF:0000033	MODIFY	Summary: SecB does bind unfolded proteins, but GO:0051082 (unfolded protein binding) under-represents the actual molecular function. SecB is not merely a passive binder of unfolded proteins; it actively carries unfolded precursors from the ribosome/cytosol to SecA at the membrane (PMID:2170023, PMID:16962134). GO:0140309 (unfolded protein holdase activity) better captures this carrier/escort function. Reason: SecB is a canonical example of a protein carrier chaperone. It binds unfolded preproteins and escorts them to SecA at translocation sites. Crane et al. mapped the path of unfolded precursor on SecB surface and described a "model for transfer of the ligand" from SecB to SecA (PMID:16962134). Hartl et al. described SecB as having "a dual function in stabilizing the precursor and in passing it on to membrane-bound SecA" (PMID:2170023). The GO term GO:0140309 "unfolded protein holdase activity" (defined as "A protein carrier activity that binds to a protein in an unfolded state and escorts it between two different cellular components") precisely describes SecB function. GO:0051082 is now formally obsolete, and the carrier term is the correct replacement. Propagation Review Root cause: SOURCE STALE OR MISSING Sources checked: PANTHER:PTN002199630 · PANTHER:PTN002199630 SOURCE STALE OR MISSING Current PTHR36918 PAINT no longer serializes obsolete GO:0051082 at this node. UniProtKB:P0AG86 · SecB SOURCE STALE OR MISSING SecB is the historical descendant evidence; direct studies support the carrier-holdase replacement. Proposed replacements: unfolded protein holdase activity Supporting Evidence: PMID:16962134 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, a peripheral component of the membrane translocon. At the translocon the ligand is passed from SecB to SecA and subsequently through the SecYEG channel. PMID:2170023 SecB has a dual function in stabilizing the precursor and in passing it on to membrane-bound SecA, the next step in the pathway. SecA itself is bound to the membrane by its affinity (Kd approximately 4 x 10(-8) M) for SecY/E and for acidic lipids. PMID:27501151 SecB is responsible for maintaining secretory proteins in an unfolded, secretion-competent state7–10, as well as for their targeted delivery to the SecA ATPase7,11. file:projects/UNFOLDED_PROTEIN_BINDING.md GO:0051082 is now formally obsolete file:ECOLI/SecB/SecB-deep-research-falcon.md SecB is classically defined as an export chaperone / holdase
GO:0070678 preprotein binding	IBA GO_REF:0000033	ACCEPT	Summary: SecB binds specifically to precursor (preprotein) forms of exported proteins in vivo and in vitro (PMID:2664780). Kumamoto showed that SecB associates with precursor forms of MBP, LamB, and OmpA but not cytoplasmic beta-galactosidase (PMID:2664780). This substrate-recognition facet is subsumed by the carrier-holdase core function. Reason: Preprotein binding is a well-characterized substrate-recognition facet of SecB's core carrier-holdase function rather than a separate core function. The IBA annotation is strongly supported by experimental data showing SecB-preprotein complexes in vivo (PMID:2664780) and the extensive characterization of SecB substrates (UniProt lists DegP, FhuA, FkpA, GBP, LamB, MalE, OmpA, OmpF, OmpT, OmpX, OppA, PhoE, TolB, TolC and others). Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002199630 · PANTHER:PTN002199630 SUPPORTS TRANSFER Current PTHR36918 PAINT retains GO:0070678 at this ancestral node. UniProtKB:P0AG86 · SecB SUPPORTS TRANSFER SecB itself is the descendant evidence and has direct preprotein-binding evidence. Supporting Evidence: PMID:2664780 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. In contrast, the cytoplasmic protein beta-galactosidase was not found in association with SecB. PMID:16352602 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.
GO:0005737 cytoplasm	IEA GO_REF:0000120	MODIFY	Summary: SecB is a cytoplasmic/cytosolic protein. This IEA annotation to cytoplasm is broader than the IBA/IDA annotations to cytosol (GO:0005829) but is not incorrect. Reason: Cytoplasmic localization is correct but less informative than the directly supported cytosol localization. Replace this broad electronic mapping with GO:0005829, which is already present in separate IBA and IDA rows. Proposed replacements: cytosol
GO:0006457 protein folding	IEA GO_REF:0000104	REMOVE	Summary: SecB is annotated to protein folding via automated transfer from UniRule. However, SecB is an anti-folding chaperone: its function is to PREVENT folding, not to assist in it. SecB maintains proteins in an unfolded state for translocation (PMID:2834066, PMID:2848249, PMID:18048690). Reason: SecB is functionally opposite to a protein folding chaperone. While GroEL/DnaK assist in proper folding, SecB specifically prevents folding. Collier et al. described SecB's function as "antifolding activity" (PMID:2834066). Bechtluft et al. showed SecB "completely prevent stable tertiary contacts" (PMID:18048690). Weiss et al. demonstrated SecB "retards folding" (PMID:2848249). The correct biological process annotation is GO:0036506 "maintenance of unfolded protein" (already present). The protein folding annotation is misleading. Supporting Evidence: PMID:2834066 The antifolding activity of SecB promotes the export of the E. coli maltose-binding protein. PMID:18048690 Interactions with SecB completely prevent stable tertiary contacts in the core structure
GO:0015031 protein transport	IEA GO_REF:0000120	MODIFY	Summary: SecB is involved in the transport of preproteins to the membrane for translocation. This IEA annotation to the broad term protein transport is acceptable as a general description, though the more specific GO:0043952 (protein transport by the Sec complex) is present and more informative. Reason: The broad protein-transport mapping is biologically sound but less informative than SecB's established role in transport by the Sec complex. Replace it with GO:0043952, which is already present in separate IBA and IMP rows. Proposed replacements: protein transport by the Sec complex
GO:0051082 unfolded protein binding	IEA GO_REF:0000002	MODIFY	Summary: This IEA annotation to unfolded protein binding from InterPro is the same term as the IBA annotation above. The same reasoning applies: SecB is more accurately described as having unfolded protein holdase activity (GO:0140309) rather than mere binding. Reason: Same rationale as the IBA annotation for GO:0051082. SecB does not merely bind unfolded proteins; it actively carries them to SecA. GO:0140309 (unfolded protein holdase activity) is the appropriate replacement. Proposed replacements: unfolded protein holdase activity Supporting Evidence: PMID:16962134 SecB delivers its ligand to export sites through its specific binding to SecA, a peripheral component of the membrane translocon. file:projects/UNFOLDED_PROTEIN_BINDING.md GO:0051082 is now formally obsolete
GO:0051262 protein tetramerization	IEA GO_REF:0000002	KEEP AS NON CORE	Summary: SecB forms a homotetramer (dimer of dimers) as confirmed by crystal structure (PMID:14643199) and biochemical characterization (PMID:2649892). This IEA annotation is consistent with experimental evidence. Reason: SecB is a well-characterized homotetramer. Watanabe and Blobel determined SecB is "a 64-kDa tetramer consisting of four identical 16-kDa subunits" (PMID:2649892). The crystal structure confirms the dimer-of-dimers architecture (UniProt cites PubMed:14643199, PubMed:27501151). While tetramerization is structural rather than a core evolved function, the annotation is factually accurate. Supporting Evidence: PMID:2649892 The purified factor amounts to 0.08% of the cytosolic proteins and is a 64-kDa tetramer consisting of four identical 16-kDa subunits.
GO:0005515 protein binding	IPI PMID:15690043 Interaction network containing conserved and essential prote...	KEEP AS NON CORE	Summary: High-throughput affinity purification/mass spectrometry study identified SecB interactions with CpxR and SecA (PMID:15690043). The annotation to generic "protein binding" is uninformative; more specific terms exist. Reason: The two IPI rows record observed SecB interactions with CpxR and SecA. They are not contradicted, but generic protein binding is uninformative and non-core. SecA binding is mechanistically coherent with carrier-holdase function; CpxR binding is a high-throughput observation of uncertain functional significance. The cached record is abstract-only and its quote describes the global method, so the exact GOA partners are retained with curator deference. Supporting Evidence: PMID:15690043 648 could be purified to homogeneity and their interacting protein partners identified by mass spectrometry
GO:0005515 protein binding	IPI PMID:19402753 Global functional atlas of Escherichia coli encompassing pre...	KEEP AS NON CORE	Summary: Large-scale E. coli functional atlas study (PMID:19402753) showing SecB-CpxR interaction. Same uninformative generic binding annotation. Reason: The CpxR interaction is a high-throughput IPI observation and is not contradicted, but generic protein binding is uninformative and non-core. The full cached paper describes the systems-wide interaction resource rather than independently establishing a SecB-CpxR mechanism, so the exact GOA partner is retained with curator deference. Supporting Evidence: PMID:19402753 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
GO:0005515 protein binding	IPI PMID:21037004 Orientation of SecA and SecB in complex, derived from disulf...	KEEP AS NON CORE	Summary: Suo et al. used disulfide cross-linking to determine the orientation of SecA and SecB in complex (PMID:21037004). This demonstrates the specific SecA-SecB interaction that is central to SecB carrier function. The annotation to generic "protein binding" is uninformative. Reason: This study characterizes the SecB-SecA interaction in detail, which is better captured by the carrier activity and preprotein binding annotations. Generic "protein binding" does not convey the functional significance. Supporting Evidence: PMID:21037004 The tetrameric cytoplasmic chaperone SecB binds to precursors of exported proteins before they can become stably folded and delivers them to SecA.
GO:0036506 maintenance of unfolded protein	IMP PMID:2834066 The antifolding activity of SecB promotes the export of the ...	ACCEPT	Summary: Collier et al. demonstrated the antifolding activity of SecB in vivo using genetic approaches. SecB- cells showed defective MBP export that was suppressed by mutations affecting MBP folding, and the rate of MBP folding was retarded in the presence of excess SecB (PMID:2834066). Reason: This is strong experimental evidence (IMP) for SecB's core antifolding function. The genetic suppression experiments directly demonstrate that SecB's role is to prevent premature folding of export substrates. This is a core function. Supporting Evidence: PMID:2834066 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; export of a mutant MBP that is accomplished in a strictly posttranslational mode was totally blocked in SecB- cells; and the rate of folding of wild-type MBP synthesized in vitro was found to be accelerated when SecB was absent and greatly retarded when excess SecB was present.
GO:0036506 maintenance of unfolded protein	IDA PMID:2848249 Purified secB protein of Escherichia coli retards folding an...	ACCEPT	Summary: Weiss et al. purified SecB and demonstrated directly that it retards folding of precursor MBP in vitro and promotes membrane translocation. Purified SecB both retarded folding and prolonged translocation competence (PMID:2848249). Reason: Direct biochemical demonstration of SecB antifolding activity using purified protein. This IDA evidence is strong support for maintenance of unfolded protein as a core function. Supporting Evidence: PMID:2848249 The purified protein also quantitatively retarded folding of precursor MBP into a stable, protease-resistant conformation in the absence of membranes. Finally, the inclusion of excess purified SecB in a SecB+ in vitro system significantly prolonged the time in which precursor MBP remained competent for posttranslational import into membrane vesicles.
GO:0005515 protein binding	IPI PMID:15811382 Asymmetric binding between SecA and SecB two symmetric prote...	KEEP AS NON CORE	Summary: Randall et al. characterized the asymmetric binding between SecA and SecB, showing that SecB C-terminal alpha-helices bind in the SecA dimer interface (PMID:15811382). This documents the specific SecA-SecB interaction central to the carrier/delivery function. Reason: The specific SecB-SecA interaction studied here is functionally meaningful and central to the carrier function, but generic "protein binding" does not convey this. The carrier activity and preprotein binding annotations better capture the functional significance. Per curation guidelines, protein binding is uninformative. Supporting Evidence: PMID:15811382 SecB also demonstrates specific recognition of, and binding to, SecA. SecB with the precursor tightly bound enters an export-active complex with SecA and must pass the ligand to SecA at the translocon in the membrane.
GO:0005515 protein binding	IPI PMID:2170023 The binding cascade of SecB to SecA to SecY/E mediates prepr...	KEEP AS NON CORE	Summary: Hartl et al. characterized the SecB-SecA-SecYEG binding cascade and determined binding affinities (PMID:2170023). This is a foundational paper for understanding SecB's carrier function. The annotation to generic "protein binding" is uninformative. Reason: This landmark study defines the binding cascade that constitutes SecB's carrier activity. Generic "protein binding" fails to capture this. The carrier activity and preprotein binding annotations are more informative. Supporting Evidence: PMID:2170023 SecB has a dual function in stabilizing the precursor and in passing it on to membrane-bound SecA, the next step in the pathway.
GO:0070678 preprotein binding	IDA PMID:2664780 Escherichia coli SecB protein associates with exported prote...	ACCEPT	Summary: Kumamoto showed that SecB associates with precursor forms of exported proteins (MBP, LamB, OmpA) in vivo, and that these complexes are transient intermediates in the export pathway (PMID:2664780). This is direct experimental evidence for preprotein binding. Reason: Strong IDA evidence for the substrate-recognition facet of SecB's core carrier function. SecB specifically recognizes and binds preprotein forms of exported proteins, but this facet is subsumed by the carrier-holdase core function. Supporting Evidence: PMID:2664780 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. In contrast, the cytoplasmic protein beta-galactosidase was not found in association with SecB. Pulse-chase analysis showed that the SecB-precursor MBP complex was short lived, as expected for a complex that represents an intermediate in the protein-export pathway. PMID:16352602 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.
GO:0005515 protein binding	IPI PMID:9321390 The molecular chaperone SecB is released from the carboxy-te...	KEEP AS NON CORE	Summary: Fekkes et al. identified the SecB binding site on SecA (the extreme C-terminal 22 residues) and showed SecB is released upon ATP binding by SecA (PMID:9321390). This characterizes the mechanistic detail of the SecB-SecA handoff. Reason: This important mechanistic study defines the SecB-SecA interaction site and the release mechanism. However, annotation to generic "protein binding" is uninformative. The carrier activity annotation better captures this delivery/handoff function. Supporting Evidence: PMID:9321390 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. ... SecB is released from this site at the onset of translocation.
GO:0008104 intracellular protein localization	IMP PMID:6403503 Mutations in a new gene, secB, cause defective protein local...	MODIFY	Summary: Kumamoto and Beckwith identified secB mutants with defective protein localization, showing SecB is required for proper localization of MBP and OmpF (PMID:6403503). This is the founding paper for SecB function. Reason: The mutant phenotype supports targeting of exported proteins but this broad localization term obscures the mechanism. Replace it with GO:0006605 protein targeting, which is already present as a separate accepted IMP row. Proposed replacements: protein targeting Supporting Evidence: PMID:6403503 These secB mutants were defective in the localization of maltose-binding protein and, in at least one case, OmpF protein. Double mutants with lesions in both secA and secB had strong defects in the secretion of maltose-binding protein and OmpF protein. PMID:16352602 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.
GO:0051082 unfolded protein binding	IDA PMID:16962134 Sites of interaction of a precursor polypeptide on the expor...	MODIFY	Summary: Crane et al. used site-directed spin labeling and EPR to map the binding pathway of unfolded precursor galactose-binding protein on SecB (PMID:16962134). They showed the precursor makes contact with a large portion of the SecB surface and established a model for transfer of the ligand from SecB to SecA. Reason: While this paper confirms SecB binds unfolded proteins, the study explicitly describes the delivery/transfer function: "SecB delivers its ligand to export sites through its specific binding to SecA" and discusses "a model for transfer of the ligand." This is carrier activity, not mere binding. GO:0140309 (unfolded protein holdase activity) captures the complete function. Proposed replacements: unfolded protein holdase activity Supporting Evidence: PMID:16962134 Export of protein into the periplasm of Escherichia coli via the general secretory system requires that the transported polypeptides be devoid of stably folded tertiary structure. 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, a peripheral component of the membrane translocon. At the translocon the ligand is passed from SecB to SecA and subsequently through the SecYEG channel. file:projects/UNFOLDED_PROTEIN_BINDING.md GO:0051082 is now formally obsolete
GO:0051082 unfolded protein binding	IMP PMID:18048690 Direct observation of chaperone-induced changes in a protein...	MODIFY	Summary: Bechtluft et al. used optical tweezers and molecular dynamics to show SecB prevents stable tertiary contacts in MBP and retains it in a molten-globule-like state (PMID:18048690). This demonstrates the holdase activity that is part of the carrier function. Reason: This paper directly establishes SecB antifolding/holdase behavior. The carrier-specific scope of GO:0140309 additionally depends on independent studies showing delivery of SecB-bound preproteins to SecA at membrane export sites (PMID:2170023, PMID:16962134). Together these support the replacement. Proposed replacements: unfolded protein holdase activity Supporting Evidence: PMID:18048690 It appears that SecB only binds to the extended or molten globulelike structure and retains MBP in this latter state. Thus during MBP translocation, no energy is required to disrupt stable tertiary interactions. PMID:2170023 SecB has a dual function in stabilizing the precursor and in passing it on to membrane-bound SecA, the next step in the pathway. file:projects/UNFOLDED_PROTEIN_BINDING.md GO:0051082 is now formally obsolete
GO:0005829 cytosol	IDA PMID:18304323 Protein abundance profiling of the Escherichia coli cytosol.	ACCEPT	Summary: Ishihama et al. identified SecB in the cytosolic proteome of E. coli by mass spectrometry (PMID:18304323). Direct experimental evidence for cytosolic localization. Reason: Proteomic identification of SecB in the cytosolic fraction is direct evidence for cytosol localization. Supporting Evidence: PMID:18304323 we identified 1103 proteins from the cytosolic fraction of the Escherichia coli strain MC4100
GO:0005829 cytosol	IDA PMID:2649892 Cytosolic factor purified from Escherichia coli is necessary...	ACCEPT	Summary: Watanabe and Blobel purified SecB as a cytosolic factor required for preprotein translocation (PMID:2649892). This is foundational evidence for SecB cytosolic localization. Reason: SecB was originally purified as a cytosolic factor, providing direct evidence for cytosol localization. Supporting Evidence: PMID:2649892 We have purified to homogeneity a cytosolic factor from Escherichia coli that is required for the translocation of a preprotein into inverted vesicles of the E. coli plasma membrane.
GO:0006605 protein targeting	IMP PMID:6403503 Mutations in a new gene, secB, cause defective protein local...	ACCEPT	Summary: SecB mutations cause defective protein targeting/localization. The original secB mutants showed pleiotropic defects in secretion of envelope proteins (PMID:6403503). Reason: SecB is essential for targeting a subset of preproteins to the Sec translocon. The GO:0006605 definition ("targeting specific proteins to particular regions of the cell") accurately describes SecB's role in directing preproteins to the inner membrane for translocation. This is consistent with but slightly different from the protein transport annotations. Supporting Evidence: PMID:6403503 We isolated a new class of Escherichia coli mutants with pleiotropic defects in protein secretion. ... the selection also yielded mutants with mutations in a new locus, which was designated secB. PMID:16352602 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.
GO:0015031 protein transport	IMP PMID:6403503 Mutations in a new gene, secB, cause defective protein local...	MODIFY	Summary: SecB mutations cause defective protein transport across the inner membrane (PMID:6403503). This is a broader term that encompasses the Sec-complex-specific annotation. Reason: The mutant phenotype supports protein transport, but SecB acts specifically in the Sec pathway. Replace this broad term with GO:0043952, which is already present in separate IBA and IMP rows. Proposed replacements: protein transport by the Sec complex Supporting Evidence: PMID:6403503 These secB mutants were defective in the localization of maltose-binding protein and, in at least one case, OmpF protein.
GO:0043952 protein transport by the Sec complex	IMP PMID:6403503 Mutations in a new gene, secB, cause defective protein local...	ACCEPT	Summary: The original secB mutant identification showed defective protein secretion, placing SecB in the Sec-dependent export pathway (PMID:6403503). Later work confirmed SecB functions specifically in the Sec pathway. Reason: The original paper identifies secB as a gene required for protein secretion alongside secA. While the original paper did not explicitly name the "Sec complex," subsequent work established SecB as a dedicated component of the Sec pathway. The IMP annotation from EcoliWiki is appropriate. Supporting Evidence: PMID:6403503 The properties of secB mutants suggest that the secB product could be a component of the E. coli secretory apparatus.

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Existing Annotations Review

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