algK encodes an outer-membrane-anchored periplasmic lipoprotein of the alginate biosynthesis/export machinery. AlgK is a TPR/Sel1-like repeat scaffold protein (not a catalytic polymerase) that organizes the trans-envelope alginate secretion complex, connecting the outer-membrane export channel AlgE with the periplasmic modification enzyme AlgX and the inner-membrane polymerization module (Alg8/Alg44), and protecting nascent polymer from periplasmic degradation. KT2440-specific wet-lab data are lacking; function is inferred from the conserved AlgK family (chiefly P. aeruginosa) plus a P. putida AlgK-AlgX complex structure.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0009279 cell outer membrane | IEA GO_REF:0000044 | ACCEPT | Summary: algK is correctly localized to the cell outer membrane. Reason: AlgK is an outer-membrane/periplasmic-side alginate assembly factor, so the outer-membrane location is intrinsic to the core pathway role. Supporting Evidence: file:PSEPK/algK/algK-uniprot.txt SUBCELLULAR LOCATION: Cell outer membrane file:PSEPK/algK/algK-goa.tsv GO:0009279 cell outer membrane file:PSEPK/algK/algK-deep-research-falcon.md Periplasmic, tethered to the **outer membrane** via N-terminal lipidation file:PSEPK/algK/algK-deep-research-falcon.md in vivo lipidation** was confirmed by palmitate labeling, - AlgK localized to **outer-membrane–enriched fractions** by sucrose-gradient fractionation, |
| GO:0042121 alginic acid biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: AlgK should retain the alginic acid biosynthetic process annotation as the correct parent process, but its role is as a non-catalytic scaffold within the synthase-dependent alginate export apparatus, not as the mannuronate polymerase. Reason: UniProt places AlgK in the alginate biosynthesis pathway, which the falcon deep research corroborates by positioning AlgK in the trans-envelope alginate biosynthesis/export apparatus. The mechanistic literature (chiefly P. aeruginosa, plus a P. putida AlgK-AlgX complex structure) makes clear AlgK is a TPR/Sel1-like scaffold lipoprotein required for assembly/stability of the export machinery rather than the enzyme that polymerizes mannuronate (that activity is Alg8/Alg44). The UniProt "May be involved in the polymerization of mannuronate" statement is an ECO:0000250 by-similarity inference and should be read as pathway membership, not a demonstrated catalytic polymerase function. GO:0042121 is retained as the appropriate broad process; KT2440-specific experimental confirmation is still lacking. Supporting Evidence: file:PSEPK/algK/algK-uniprot.txt May be involved in the polymerization of mannuronate to file:PSEPK/algK/algK-uniprot.txt PATHWAY: Glycan biosynthesis; alginate biosynthesis file:PSEPK/algK/algK-goa.tsv GO:0042121 alginic acid biosynthetic process file:PSEPK/algK/algK-deep-research-falcon.md AlgK functions within the **synthase-dependent alginate biosynthesis/export pathway**, in the trans-envelope apparatus spanning IM (Alg8/Alg44) → periplasm (AlgX/AlgG/AlgL etc.) → OM (AlgE). file:PSEPK/algK/algK-deep-research-falcon.md AlgK is not an enzyme catalyzing a chemical reaction; rather, it is a **non-catalytic assembly/scaffolding factor** essential for efficient alginate polymer production and export. |
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Download this section (compressed HTML)Q: Is the AlgK scaffold/conduit role characterized in P. aeruginosa (and the P. putida AlgK-AlgX complex structure) fully conserved in P. putida KT2440 (PP_1285), given that no KT2440-specific wet-lab study was found?
Q: Does P. putida AlgK organize the same AlgEKX outer-membrane complex in vivo, and is the AlgK-AlgX interface (AlgX N-terminus to AlgK TPRs 9-10) required for alginate export in KT2440?
Experiment: Generate a KT2440 algK deletion and complement strain and measure alginate polymer production, polymer molecular weight, and AlgE outer-membrane localization, testing whether loss of AlgK yields low-molecular-weight uronic acids and AlgE mislocalization as seen in P. aeruginosa.
Type: alginate production and AlgE localization assay
Experiment: Co-immunoprecipitation and/or in vitro reconstitution to confirm the AlgK-AlgX and AlgK-AlgE interactions in KT2440 and verify the trans-envelope secretion complex membership predicted by orthology.
Type: protein-protein interaction and complex-assembly assay
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