| Topic | Concise finding | Quantitative / specific details | Key citations, DOI/URL, year |
|---|---|---|---|
| Verified target identity | Target matches **MutS DNA mismatch repair protein**: **UniProt Q88ME7**, gene **mutS**, ordered locus **PP_1626**, organism **Pseudomonas putida KT2440**; literature on *P. putida* MMR consistently treats **MutS** as the mismatch-recognition factor acting with **MutL** in an abridged, **MutH-lacking** bacterial MMR system. Conserved family/domain assignment is consistent with a canonical **MutS DNA mismatch repair family** ATPase/sliding-clamp protein. | *P. putida* encodes **MutS** and **MutL** but lacks a bona fide **MutH** homolog; therefore pathway inference should follow MutH-independent bacterial MMR, not the full *E. coli* 3-protein methyl-directed pathway. | (pqac-00000000, pqac-00000015, pqac-00000017) Aparicio et al., *Environ. Microbiol.* DOI: https://doi.org/10.1111/1462-2920.14814 (2020); Collingwood et al., *Biomolecules* DOI: https://doi.org/10.3390/biom14111442 (2024) |
| Core MutS mechanism | MutS is the **primary mismatch sensor**. It scans dsDNA in an **ADP-bound/open** state, binds mismatches or small IDLs, then undergoes **ADP→ATP exchange**; binding of **two ATP molecules** converts the dimer to a **closed/sliding-clamp** state that leaves the mismatch and diffuses on DNA to **recruit/load MutL**. ATP hydrolysis resets the complex after encountering ssDNA/gaps or breaks. | MutS binds mismatched DNA with ~**10–20-fold** higher affinity than matched DNA; ATP can enhance mismatch binding up to **~29-fold** for some mismatches; ADP reduces clamp-formation kinetics; example for CC mismatch: **k2 = 0.007 ± 0.001 s⁻¹** with 1 mM ADP vs **0.57 ± 0.01 s⁻¹** with 1 mM ATP. DNA is kinked by ~**60°** upon mismatch recognition. | (pqac-00000001, pqac-00000003, pqac-00000004, pqac-00000005, pqac-00000006, pqac-00000020, pqac-00000021, pqac-00000022) Zarb (2024, single-molecule thesis/manuscript in retrieved corpus); Waters & Spratt, DOI: https://doi.org/10.3390/ijms25031676 (2024) |
| P. putida mismatch-recognition hierarchy | In *P. putida*, MMR shows a clear mismatch-recognition hierarchy rather than equal correction of all mismatches. This hierarchy was inferred by ssDNA recombineering in WT, **ΔmutS**, and transient **mutL E36K** inhibition backgrounds. | Reported hierarchy: **A:G < C:C < G:A < C:A, A:A, G:G, T:T, T:G, A:C, C:T < G:T, T:C**. This is the key organism-specific specificity result available for KT2440/EM42-related strains. | (pqac-00000000, pqac-00000015) Aparicio et al., DOI: https://doi.org/10.1111/1462-2920.14814 (2020) |
| P. putida mutator phenotypes / MMR perturbation | Conditional inhibition of MMR in *P. putida* was implemented with plasmid-borne **dominant-negative mutL E36K** devices; these transiently elevate mutation frequency and accelerate phenotype emergence. A cited KT2440 **ΔmutS** strain shows a much stronger constitutive mutator phenotype. | **KT2440/pS2311M**: **438-fold** increase in RifR and **10-fold** increase in StrR vs control when induction ended in early exponential phase. **KT2440/pS2514M**: **45-fold** RifR and **14-fold** StrR increases. A cited prior study found **ΔmutS KT2440 ~1000-fold** higher RifR frequency vs WT. Mutation frequencies were reported as mutants per **10⁹ viable cells**. | (pqac-00000008, pqac-00000009, pqac-00000010, pqac-00000011, pqac-00000013) Fernández-Cabezón et al., *ACS Synth. Biol.* DOI: https://doi.org/10.1021/acssynbio.1c00031 (2021) |
| Action-at-a-distance models | Recent expert synthesis concludes that communication between a mismatch-bound MutS complex and distant incision/excision sites can be explained by three non-exclusive model classes: **tracking/sliding**, **DNA looping**, and **oligomerization/bridging**. In MutH-lacking bacteria, MutL-family endonuclease activity substitutes for MutH-mediated nicking. | Sliding-clamp models: ATP-bound MutS diffuses away from the mismatch and recruits MutL. Looping models: ATP-driven translocation/extrusion brings distant sites together. Oligomerization models: MutS remains mismatch-bound while MutL/other factors bridge distance. Review emphasizes that mechanisms likely differ by organism and may coexist. | (pqac-00000016, pqac-00000017, pqac-00000018, pqac-00000019) Collingwood et al., *Biomolecules* DOI: https://doi.org/10.3390/biom14111442 (2024) |
| Pathway context and localization | Functional localization is **intracellular, chromosome-associated (nucleoid/DNA-bound)**: MutS acts on newly replicated genomic DNA where replication errors arise, then coordinates with MutL and downstream excision/resynthesis factors. For *P. putida*, localization is inferred from conserved bacterial MutS biochemistry and organism-specific MMR genetics rather than direct localization imaging in the retrieved sources. | In canonical bacterial descriptions, downstream factors include **MutL**, helicase/excision factors such as **UvrD** and exonucleases, followed by DNA polymerase and ligase. In MutH-lacking systems, strand discrimination relies on **MutL endonuclease/nicks** or pre-existing discontinuities rather than MutH cleavage at hemimethylated GATC sites. | (pqac-00000000, pqac-00000007, pqac-00000017, pqac-00000018, pqac-00000023) Aparicio et al., DOI: https://doi.org/10.1111/1462-2920.14814 (2020); Collingwood et al., DOI: https://doi.org/10.3390/biom14111442 (2024); Waters & Spratt, DOI: https://doi.org/10.3390/ijms25031676 (2024) |


*Table: This table condenses the verified identity, conserved mechanism, organism-specific mismatch preferences, quantitative mutator phenotypes, and current mechanistic models relevant to Pseudomonas putida KT2440 MutS (Q88ME7/PP_1626). It separates direct P. putida evidence from broader bacterial MutS mechanism needed for functional annotation.*