opgG encodes a Sec-exported periplasmic OpgD/OpgG-family beta-1,2-glucanase that supports osmoregulated periplasmic glucan production by processing the beta-glucan backbone with the OpgH glucosyltransferase.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005975 carbohydrate metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: Carbohydrate metabolism is a broad parent term for OpgG's role in osmoregulated periplasmic glucan biosynthesis. Reason: UniProt places OpgG specifically in the osmoregulated periplasmic glucan biosynthesis pathway; the broad carbohydrate metabolic process term should be replaced by the specific OPG biosynthesis term. Proposed replacements: osmoregulated periplasmic glucan biosynthetic process Supporting Evidence: file:PSEPK/opgG/opgG-uniprot.txt FUNCTION: Involved in the biosynthesis of osmoregulated periplasmic file:PSEPK/opgG/opgG-uniprot.txt PATHWAY: Glycan metabolism; osmoregulated periplasmic glucan (OPG) file:PSEPK/opgG/opgG-goa.tsv GO:0005975 carbohydrate metabolic process |
| GO:0009250 glucan biosynthetic process | IEA GO_REF:0000104 | MODIFY | Summary: Glucan biosynthesis is correct but should be made specific to osmoregulated periplasmic glucan biosynthesis. Reason: UniProt assigns OpgG to OPG biosynthesis, and GO:1900727 captures this pathway more specifically than generic glucan biosynthesis. Proposed replacements: osmoregulated periplasmic glucan biosynthetic process Supporting Evidence: file:PSEPK/opgG/opgG-uniprot.txt PATHWAY: Glycan metabolism; osmoregulated periplasmic glucan (OPG) file:PSEPK/opgG/opgG-goa.tsv GO:0009250 glucan biosynthetic process |
| GO:0016051 carbohydrate biosynthetic process | IEA GO_REF:0000002 | MODIFY | Summary: Carbohydrate biosynthesis is a broad parent term for OpgG's role in OPG biosynthesis. Reason: The OpgG-specific process is osmoregulated periplasmic glucan biosynthesis, so the broad carbohydrate biosynthetic process term should be replaced by GO:1900727. Proposed replacements: osmoregulated periplasmic glucan biosynthetic process Supporting Evidence: file:PSEPK/opgG/opgG-uniprot.txt FUNCTION: Involved in the biosynthesis of osmoregulated periplasmic file:PSEPK/opgG/opgG-goa.tsv GO:0016051 carbohydrate biosynthetic process |
| GO:0030246 carbohydrate binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Carbohydrate binding is plausible for OpgG but is secondary to its inferred beta-1,2-glucanase activity. Reason: InterPro supports carbohydrate binding for the OpgD/OpgG-family protein, but primary biochemical work on E. coli OpgG/OpgD identifies this family as GH186 beta-1,2-glucanases. Binding should be retained as a supporting, non-core activity rather than the primary molecular function. Supporting Evidence: file:PSEPK/opgG/opgG-goa.tsv GO:0030246 carbohydrate binding file:PSEPK/opgG/opgG-uniprot.txt Belongs to the OpgD/OpgG family PMID:37735577 EcOpgG was found to hydrolyze Ξ²-1,2-glucans; however, the catalytic velocity was very low |
| GO:0033913 glucan endo-1,2-beta-glucosidase activity | ISS PMID:37735577 Identification of enzymatic functions of osmo-regulated peri... | NEW | Summary: OpgG's core molecular function is inferred to be beta-1,2-glucanase activity. Reason: Primary biochemical and structural work on E. coli OpgG/OpgD-family orthologs supports GH186 beta-1,2-glucanase activity, and the P. putida protein has strong sequence, domain, signal-peptide, and opgGH operon support for ISS transfer of the same periplasmic OPG-processing role. Supporting Evidence: PMID:37735577 EcOpgG was found to hydrolyze Ξ²-1,2-glucans; however, the catalytic velocity was very low PMID:37735577 EcOpgG also showed the same substrate specificity toward the polysaccharides as that of EcOpgD. file:PSEPK/opgG/opgG-deep-research-openscientist.md Global NeedlemanβWunsch alignment of Q88D03 (559 aa) gave **63.6% identity (357/561 aligned positions)** to the biochemically and structurally characterized E. coli OpgG (P33136) and **66.4% identity (383/577)** to P. aeruginosa OpgG (Q9HUA5). file:PSEPK/opgG/opgG-deep-research-openscientist.md The exact in-vivo cut/branch chemistry OpgG performs during OPG maturation remains to be pinned down, but the enzyme class is now defined. |
| GO:0030288 outer membrane-bounded periplasmic space | IEA GO_REF:0000118 | ACCEPT | Summary: Outer membrane-bounded periplasmic space is the appropriate location for Gram-negative OpgG. Reason: UniProt places OpgG in the periplasm with an N-terminal signal peptide, and TreeGrafter provides the Gram-negative-specific periplasmic compartment term. Supporting Evidence: file:PSEPK/opgG/opgG-uniprot.txt SUBCELLULAR LOCATION: Periplasm file:PSEPK/opgG/opgG-uniprot.txt FT SIGNAL 1..17 file:PSEPK/opgG/opgG-goa.tsv GO:0030288 outer membrane-bounded periplasmic space |
| GO:0042597 periplasmic space | IEA GO_REF:0000120 | MODIFY | Summary: Periplasmic space is correct but less specific than the Gram-negative outer membrane-bounded periplasmic space term. Reason: OpgG is a signal-peptide-bearing periplasmic protein in a Gram-negative bacterium; GO:0030288 is the more precise concurrent location term. Proposed replacements: outer membrane-bounded periplasmic space Supporting Evidence: file:PSEPK/opgG/opgG-uniprot.txt SUBCELLULAR LOCATION: Periplasm file:PSEPK/opgG/opgG-goa.tsv GO:0042597 periplasmic space |
| GO:0051274 beta-glucan biosynthetic process | IEA GO_REF:0000118 | MODIFY | Summary: Beta-glucan biosynthesis is correct but OPG biosynthesis is the more specific pathway context for OpgG. Reason: OpgG is assigned to osmoregulated periplasmic glucan biosynthesis; GO:1900727 captures that pathway more specifically than beta-glucan biosynthetic process. Proposed replacements: osmoregulated periplasmic glucan biosynthetic process Supporting Evidence: file:PSEPK/opgG/opgG-uniprot.txt PATHWAY: Glycan metabolism; osmoregulated periplasmic glucan (OPG) file:PSEPK/opgG/opgG-goa.tsv GO:0051274 beta-glucan biosynthetic process |
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Download this section (compressed HTML)Q: What exact in-vivo cut, trimming, or branch-shaping reaction does KT2440 OpgG perform during OPG maturation?
Q: How does OpgG's beta-1,2-glucanase activity coordinate with the inner-membrane OpgH glucosyltransferase?
Experiment: Compare OPG amount and size distribution in wild-type, opgG, opgH, and opgGH mutant strains under low-osmolarity conditions.
Type: targeted genetics and glucan profiling
Experiment: Assay purified periplasmic OpgG against defined beta-1,2-glucan oligosaccharides to confirm GH186 beta-1,2-glucanase activity and substrate-length preference.
Type: in vitro glycoside hydrolase assay
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