celB

UniProt ID: Q7CS46
Organism: Agrobacterium fabrum str. C58
Review Status: COMPLETE
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Gene Description

CelB (Atu3308) is the noncatalytic, membrane-anchored partner of cellulose synthase CelA in Agrobacterium fabrum C58. Its AcsB/BcsB-family carbohydrate-binding and flavodoxin-like domains are predicted to occupy the periplasm, with a C-terminal transmembrane anchor connecting the protein to the inner membrane. It supports cellulose synthesis and handling of the emerging glucan; glycosyl transfer and the established c-di-GMP switch reside in CelA.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0005886 plasma membrane
IEA
GO_REF:0000120
ACCEPT
Summary: Retain membrane-anchored cellulose synthase partner localization.
Reason: The target has a signal peptide and C-terminal membrane helix, the specific AcsB/BcsB family assignment, and a curated RuleBase inner-membrane location. The homolog structure independently establishes membrane-anchored periplasmic BcsB architecture.
Supporting Evidence:
file:AGRFC/celB/celB-uniprot.txt
Belongs to the AcsB/BcsB family.
PMID:23222542
BcsB is a periplasmic protein that is anchored to the inner membrane via a single, C-terminal TM-helix.
GO:0006011 UDP-alpha-D-glucose metabolic process
IEA
GO_REF:0000002
MODIFY
Summary: Replace donor-centric metabolism with the cellulose biosynthetic role.
Reason: CelB is a structural component of cellulose synthase; CelA performs UDP-glucose glycosyl transfer. BcsB-specific domains and the homolog BcsAB structure support direct participation by organizing the synthesis complex, independently of mutant necessity. GO:0030244 lies under glucan/polysaccharide biosynthesis. It is not a descendant of UDP-glucose metabolism: this is an explicit role correction, not a claimed hierarchical refinement. Same-role QuickGO checks on E. coli P37652 and P. putida Q88JL3 found the same broad donor-metabolism annotation and no cellulose-biosynthesis row. That absence is not evidence of a gap; the replacement rests on structural participation and the conserved family, not on annotation counting. No duplicate NEW process row is added, and no target GO-CAM was present in the index. Use the bacterial-context subtype GO:0090540 of cellulose biosynthesis; the term adds no new native-output or fibril criterion. CelB contributes structural support to a bacterial synthase; this is a role correction from donor metabolism, not assignment of CelA catalysis.
Supporting Evidence:
file:AGRFC/celB/celB-uniprot.txt
Belongs to the AcsB/BcsB family.
PMID:23222542
BcsB is a periplasmic protein that is anchored to the inner membrane via a single, C-terminal TM-helix.
GO:0016020 membrane
IEA
GO_REF:0000002
MODIFY
Summary: Refine membrane to plasma membrane.
Reason: The target signal peptide and C-terminal membrane anchor, together with conserved BcsB structure, identify the inner membrane. Plasma membrane is a checked descendant already present in this review.
Proposed replacements: plasma membrane
Supporting Evidence:
file:AGRFC/celB/celB-uniprot.txt
Belongs to the AcsB/BcsB family.
PMID:23222542
BcsB is a periplasmic protein that is anchored to the inner membrane via a single, C-terminal TM-helix.

Core Functions

Predicted membrane-anchored periplasmic partner that supports the CelA cellulose synthase and organizes passage of the emerging glucan. The precise C58 complex architecture has not been determined.

Cellular Locations:
Supporting Evidence:
  • file:AGRFC/celB/celB-uniprot.txt
    Belongs to the AcsB/BcsB family.
  • PMID:23222542
    BcsB is a periplasmic protein that is anchored to the inner membrane via a single, C-terminal TM-helix.

References

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Suggested Questions for Experts

Q: What contacts and stoichiometry connect CelB to CelA and other C58 type III cellulose components?

Q: Does purified C58 CelB have a demonstrable glucan-binding or other subunit-specific molecular activity?

πŸ“š Additional Documentation

Notes

(celB-notes.md)

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