| Finding/metric | Value(s) | Experimental context | Source (first author, year, journal) | URL | Notes for annotation |
|---|---:|---|---|---|---|
| Hsp82 vs Hsc82 sequence identity | 97% amino-acid identity; 16 residue differences | Comparative analysis of the two cytosolic yeast Hsp90 isoforms | Girstmair, 2019, *Nature Communications* (pqac-00000033) | https://doi.org/10.1038/s41467-019-11518-w | Confirms HSP82 belongs to the Hsp90 family and is distinct from HSC82 despite very high similarity. |
| Hsp82 baseline abundance relative to Hsc82 under nonstress conditions | Hsc82 ~10-fold higher than Hsp82 | Nonstress expression in *S. cerevisiae* | Girstmair, 2019, *Nature Communications* (pqac-00000033) | https://doi.org/10.1038/s41467-019-11518-w | Supports annotation of Hsp82 as the low-baseline, stress-inducible cytosolic Hsp90 isoform. |
| Hsp82 induction at elevated temperature | At 37°C, Hsp82 rises to levels similar to Hsc82 | Heat-induction of cytosolic Hsp90 isoforms | Rios, 2024, *Frontiers in Molecular Biosciences* (pqac-00000032) | https://doi.org/10.3389/fmolb.2024.1325590 | Key evidence that HSP82 is the heat-inducible isoform. |
| Growth supported by reduced Hsp90 expression | 1%–5% of wild-type expression still permits growth at optimal temperature, but not elevated temperature | Genetic expression reduction of yeast cytosolic Hsp90 | Rios, 2024, *Frontiers in Molecular Biosciences* (pqac-00000032) | https://doi.org/10.3389/fmolb.2024.1325590 | Indicates Hsp90 function is essential but quantitatively buffered under permissive conditions. |
| Essentiality of HSP82/HSC82 family | Single deletion viable; double disruption lethal | Classic yeast genetics of paralog pair | Kimura, 1994, *Molecular and General Genetics* (pqac-00000018) | https://doi.org/10.1007/bf00285275 | Important for functional annotation: at least one cytosolic Hsp90 isoform is required for viability. |
| Hsp82 melting temperature (Tm) | 60.4 ± 0.5 °C | Thermal stability comparison without nucleotide | Girstmair, 2019, *Nature Communications* (pqac-00000033) | https://doi.org/10.1038/s41467-019-11518-w | Reflects enhanced thermotolerance of Hsp82, consistent with stress specialization. |
| Hsc82 melting temperature (Tm) | 57.1 ± 0.2 °C | Thermal stability comparison without nucleotide | Girstmair, 2019, *Nature Communications* (pqac-00000033) | https://doi.org/10.1038/s41467-019-11518-w | Lower Tm than Hsp82 helps explain isoform specialization. |
| ATPγS effect on thermal stability | ~+3 °C for both isoforms | ATP analog binding during thermal unfolding analysis | Girstmair, 2019, *Nature Communications* (pqac-00000033) | https://doi.org/10.1038/s41467-019-11518-w | Supports ATP-dependent stabilization of the Hsp90 fold. |
| Hsc82 ATPase activity relative to Hsp82 | ~1.3-fold higher at 30°C; ~1.6-fold higher at 37°C | Isoform enzymology comparison | Girstmair, 2019, *Nature Communications* (pqac-00000003) | https://doi.org/10.1038/s41467-019-11518-w | Indicates isoform-specific ATPase tuning rather than different core family assignment. |
| Hsp82 refolding efficiency vs Hsc82 | ~29% vs ~14% full refolding events | Single-molecule mechanical assays | Girstmair, 2019, *Nature Communications* (pqac-00000003) | https://doi.org/10.1038/s41467-019-11518-w | Quantifies superior resilience/refolding behavior of stress-induced Hsp82. |
| Proteome fraction broadly affected by Hsp90 inhibition | ~10%–15% of proteins | Review of yeast Hsp90 functional impact | Rios, 2024, *Genetics* (pqac-00000030) | https://doi.org/10.1093/genetics/iyae057 | Shows Hsp90 is selective but still proteome-broad in influence. |
| Proteomics dataset size | 2,482 proteins measured (~38% of yeast proteome) | DIA-MS analysis of strains expressing wild-type or mutant Hsp90 | Rios, 2024, *Genetics* (pqac-00000030, pqac-00000034) | https://doi.org/10.1093/genetics/iyae057 | Useful benchmark for the scale of experimentally observed Hsp90-dependent proteome effects. |
| Proteins significantly altered in Hsp90 mutant dataset | 350 proteins (14% of measured set), using log2 fold change ≥ 1.5 | Quantitative proteomics of 9 Hsp90 mutants vs wild type | Rios, 2024, *Genetics* (pqac-00000030, pqac-00000034) | https://doi.org/10.1093/genetics/iyae057 | Supports annotation of Hsp90/Hsp82 as a major proteostasis hub affecting many clients/indirect targets. |
| Previously known Hsp90-linked proteins within altered set | 257/350 (~73%) | Cross-comparison of proteomic hits with prior Hsp90 literature | Rios, 2024, *Genetics* (pqac-00000030, pqac-00000034) | https://doi.org/10.1093/genetics/iyae057 | Suggests many abundance changes reflect bona fide Hsp90-connected biology. |
| Number of Hsp90 mutants analyzed in proteomics study | 9 mutants | Mutants disrupting distinct steps of the Hsp90 cycle | Rios, 2024, *Genetics* (pqac-00000030, pqac-00000034) | https://doi.org/10.1093/genetics/iyae057 | Supports state-specific/client-specific functional annotation. |
| Principal component clustering of mutant effects | 3 primary clusters | PCA of proteomic profiles from Hsp90-cycle mutants | Rios, 2024, *Genetics* (pqac-00000030, pqac-00000034) | https://doi.org/10.1093/genetics/iyae057 | Suggests distinct conformational states support distinct client pools. |
| Industrial/domestication strain panel size | 711 strains | Comparative analysis of domesticated and wild yeast robustness under Hsp90 stress | Condic, 2024, *Science* (pqac-00000024) | https://doi.org/10.1126/science.adi3048 | Strong recent evidence linking Hsp90 to real-world fermentation adaptation. |
| Number of metabolic traits screened | 12 traits | Hsp90 inhibition used as proxy for environmental/proteotoxic stress | Condic, 2024, *Science* (pqac-00000024) | https://doi.org/10.1126/science.adi3048 | Demonstrates broad metabolic phenotyping framework for Hsp90-dependent robustness. |
| Radicicol concentrations used for Hsp90 perturbation | 4 µM and 10 µM | Low and moderate Hsp90 disruption in chemical-genetic screens | Condic, 2024, *Science* (pqac-00000026) | https://doi.org/10.1126/science.adi3048 | Practical concentrations for yeast Hsp90-stress screening assays. |
| Genetic variance in maltose robustness explained by MAL gene duplications | ≥60% of genetic variance | Domestication/fermentation robustness under Hsp90 stress | Condic, 2024, *Science* (pqac-00000025) | https://doi.org/10.1126/science.adi3048 | Indicates Hsp90-buffered variation has major quantitative consequences for industrial traits. |
| Diversity sampled in domestication analysis | 73 genetic backgrounds; 10 ecological niches | Population-scale metabolic robustness analysis | Condic, 2024, *Science* (pqac-00000026) | https://doi.org/10.1126/science.adi3048 | Shows the Hsp90 effect was evaluated across broad yeast diversity. |
| Statistical significance for trait variability across isolates | F test, P = 2.0585 × 10^-8 | Variation in Hsp90-stress sensitivity across strains/traits | Condic, 2024, *Science* (pqac-00000026) | https://doi.org/10.1126/science.adi3048 | Supports that Hsp90-dependent metabolic robustness differences are highly significant. |
| Hsp90 abundance can be reduced without viability at 25°C | ~10-fold reduction tolerated at 25°C | Classic Hsp90 abundance/viability genetics | Nathan, 1999, *PNAS* (pqac-00000016) | https://doi.org/10.1073/pnas.96.4.1409 | Reinforces the idea that abundance reserve exists under permissive conditions, despite essentiality of the family. |


*Table: This table compiles key numeric findings relevant to functional annotation of yeast HSP82/Hsp90, including isoform identity, heat induction, essentiality thresholds, thermal and ATPase differences, proteome-wide effects, and recent industrial screening data.*