| Claim/Topic | Organism/Context | Key finding | Quantitative data (if any) | Source (authors, year, journal) | URL | Evidence strength (direct *P. putida* vs inferred from other bacteria/review) |
|---|---|---|---|---|---|---|
| htpG induction under NaCl osmotic stress | *Pseudomonas putida* KT2440; transcriptomics after osmotic challenge | PP_4179 (*htpG*) is strongly upregulated as a stress-protein transcript during osmotic stress. | 10.1-fold increase at T2 (60 min) after NaCl stress (pqac-00000012) | Bojanovič, D'Arrigo, Long, 2017, *Applied and Environmental Microbiology* (pqac-00000012) | https://doi.org/10.1128/AEM.03236-16 | Direct *P. putida* evidence |
| htpG induction under elevated pressure / pressure + oxygen | *Pseudomonas putida* KT2440; microarray stress-response study | PP_4179 is induced under elevated pressure and further induced under pressure plus elevated dissolved oxygen, consistent with heat-shock/chaperone stress response. | Pressure: +1.65 FC, adj. P = 1.0E-02; Pressure + oxygen: +1.92 FC, adj. P = 2.0E-02 (pqac-00000000, pqac-00000001, pqac-00000013) | Follonier et al., 2013, *Microbial Cell Factories* (pqac-00000013) | https://doi.org/10.1186/1475-2859-12-30 | Direct *P. putida* evidence |
| Heat-induction kinetics (qRT-PCR time course) | *Pseudomonas putida* KT/KT2440 heat-shock response | *htpG* mRNA is heat inducible; induction is detectable within 10 min after temperature upshift, including mild 33°C shift. At 33°C the response is transient, whereas at 40–45°C expression remains high after 30 min; pattern correlates with σ32/RpoH induction. | Time-resolved response: induction within 10 min; at 33°C transient peak then decline then rebound by 30 min; at 40–45°C sustained high levels after 30 min (pqac-00000003) | Ito et al., 2014, *MicrobiologyOpen* (pqac-00000003) | https://doi.org/10.1002/mbo3.217 | Direct *P. putida* evidence |
| Domain architecture and dimerization | General bacterial HtpG/Hsp90; structural review with *E. coli* Hsp90 as model | Bacterial HtpG is a constitutive homodimer with three conserved domains: N-terminal ATP-binding domain (NTD), middle domain (MD), and C-terminal dimerization domain (CTD). Client-binding surfaces span MD/CTD in bacterial Hsp90. | Dimeric state; three-domain architecture explicitly defined (pqac-00000004, pqac-00000005, pqac-00000014) | Wickramaratne, Wickner, Kravats, 2024, *Microbiology and Molecular Biology Reviews* (pqac-00000004, pqac-00000005, pqac-00000014) | https://doi.org/10.1128/MMBR.00176-22 | Inferred for *P. putida* from conserved bacterial HtpG/Hsp90 family/review |
| Interaction with DnaK and micromolar affinity | General bacterial HtpG/Hsp90, especially *E. coli* model | HtpG collaborates with Hsp70/DnaK and its cochaperones in client remodeling/refolding; Hsp90 and DnaK directly interact through the Hsp90 middle domain. | Hsp90–DnaK interaction reported as weak, in the low micromolar affinity range (pqac-00000006) | Wickramaratne, Wickner, Kravats, 2024, *Microbiology and Molecular Biology Reviews* (pqac-00000006) | https://doi.org/10.1128/MMBR.00176-22 | Inferred for *P. putida* from conserved bacterial HtpG/Hsp90 mechanism/review |
| No known bacterial Hsp90 cochaperone homologs | General bacterial HtpG/Hsp90 comparative review | Unlike eukaryotic Hsp90 systems, bacteria lack confirmed homologs of canonical Hsp90 cochaperones; instead, HtpG functionally collaborates with Hsp70/J-domain proteins/GrpE systems. | Qualitative claim; no bacterial homologs of eukaryotic Hsp90 cochaperones identified in the review (pqac-00000004, pqac-00000005) | Wickramaratne, Wickner, Kravats, 2024, *Microbiology and Molecular Biology Reviews* (pqac-00000004, pqac-00000005) | https://doi.org/10.1128/MMBR.00176-22 | Inferred for *P. putida* from authoritative bacterial Hsp90 review |
| ΔhtpG phenotypes relevant to stress/virulence | *Pseudomonas aeruginosa* mutant study | Loss of *htpG* affects multiple physiological and virulence-related traits, supporting a role for HtpG in stress-adaptive proteostasis beyond simple heat tolerance. | Decreased LasA protease activity, reduced biofilm formation, decreased motility, and reduced rhamnolipid/pyoverdine/pyocyanin production; defects most evident at 42°C (pqac-00000002) | Grudniak, Klecha, Wolska, 2018, *Future Microbiology* (pqac-00000002) | https://doi.org/10.2217/fmb-2017-0111 | Indirect for *P. putida*; evidence from related *Pseudomonas* species |
| Cytosolic stress chaperone role in bacteria | General bacterial HtpG/Hsp90 background | HtpG is a conserved cytosolic chaperone involved in protein folding, anti-aggregation, disaggregation, and proteostasis, especially during stress; in bacteria it works with Hsp70 systems rather than an extensive eukaryotic cochaperone network. | Hsp90-family proteins can comprise ~1–2% of cytosolic proteins in bacteria/eukaryotes discussed in review/background (pqac-00000002, pqac-00000007, pqac-00000010) | Grudniak et al., 2018, *Future Microbiology*; Wickramaratne et al., 2024, *MMBR*; Singh et al., 2024, *IJMS* (pqac-00000002, pqac-00000007, pqac-00000010) | https://doi.org/10.2217/fmb-2017-0111 ; https://doi.org/10.1128/MMBR.00176-22 ; https://doi.org/10.3390/ijms25084209 | Inferred for *P. putida* from conserved family biology and reviews |


*Table: This table compiles direct evidence for *Pseudomonas putida* KT2440 htpG/PP_4179 stress responsiveness and key conserved mechanistic features of bacterial HtpG/Hsp90. It separates species-specific observations from broader family-level inferences useful for functional annotation of UniProt Q88FB9.*