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The primary molecular function of yeast Hsp60 is as an ATP-dependent protein
folding chaperonin for mitochondrial matrix proteins, especially those imported
as unfolded precursors; it does not perform a small-molecule chemical reaction
but catalyzes conformational maturation of polypeptides.
"ATP-dependent **protein folding chaperonin** for mitochondrial matrix proteins, particularly those imported into mitochondria as unfolded precursors. (verghese2012biologyofthe pages 29-30, cabiscol2002mitochondrialhsp60resistance pages 1-1)"
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Hsp60 catalyzes conformational maturation of polypeptides by providing a protected
folding environment and coordinating substrate binding/release with ATP hydrolysis
and Hsp10 capping, rather than transforming a small-molecule substrate.
"Hsp60 does not catalyze a chemical transformation of a small molecule substrate; rather, it catalyzes **conformational maturation of polypeptides** by providing a protected folding environment and coordinating binding/release with ATP hydrolysis and Hsp10 capping."
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In yeast Hsp60 forms a 14-subunit double ring (two heptameric rings) enclosing a
cavity that accommodates clients up to ~50 kDa; imported precursors transiently
associate as incompletely folded intermediates before ATP-dependent folding/release.
"In yeast specifically, Hsp60 forms a **14-subunit double-ring (two heptameric rings)**, creating a cavity that can accommodate client proteins up to ~**50 kDa**, and imported precursor proteins transiently associate with Hsp60 as incompletely folded intermediates before ATP-dependent folding/release."
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The co-chaperonin Hsp10 (GroES-like) caps the folding cavity as a lid to create an
encapsulated folding environment, and ATP hydrolysis plus nucleotide exchange govern
substrate release and cycle reset.
"the co-chaperonin **Hsp10 (GroES-like)** caps the cavity (“lid”), enabling an encapsulated folding environment; ATP hydrolysis and nucleotide exchange govern release/reset."
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Yeast Hsp60 is synthesized as a mitochondrial precursor with an N-terminal
matrix-targeting presequence that is cleaved by the mitochondrial processing
peptidase (MPP) after residue 21, yielding the mature matrix protein.
"Yeast Hsp60 is produced as a **mitochondrial precursor** with an N-terminal matrix-targeting presequence, cleaved by MPP after residue 21, consistent with mitochondrial import and processing to a mature matrix protein."
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HSP60 is essential for viability; deletion/null mutants are inviable due to severe
mitochondrial folding defects.
"HSP60 is **essential for viability**: deletion/null mutants are inviable due to severe mitochondrial folding defects."
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Representative Hsp60-dependent yeast clients include F1-ATPase subunits, cytochrome
b2, and the Rieske Fe-S protein; conditional Hsp60 mutants accumulate insoluble
matrix aggregates.
"Representative mitochondrial proteins discussed as Hsp60-dependent/affected in yeast reviews include **F1-ATPase subunits**, **cytochrome b2**, and the **Rieske Fe–S protein**; conditional mutants can accumulate **insoluble matrix aggregates**."
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The temperature-sensitive mif4 allele (Gly298Asp) causes the ~840 kDa Hsp60 complex
to become insoluble within ~2 hours after temperature shift.
"A temperature-sensitive **mif4** allele (Gly298→Asp) has been reported to cause the existing ~**840 kDa** Hsp60 complex to become insoluble within ~2 hours after temperature shift, pelleting at 15,000×g; this phenotype is described in a chaperonin chronologue review synthesizing genetic/biochemical evidence."
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Hsp60 is induced 2-3 fold at 42 degrees C and protects Fe/S enzymes from oxidative
inactivation in a dose-dependent manner; reduced Hsp60 increases the labile iron
pool, and iron chelation partially rescues survival and oxidation phenotypes,
linking Hsp60 to oxidative-stress defense.
"The same work reports Hsp60 is induced **2–3× at 42°C** and that protection of Fe/S enzymes from oxidative inactivation is **dose-dependent** on Hsp60 levels; reduced Hsp60 increased the labile iron pool (calcein assay), and iron chelation (deferoxamine) partially rescued survival and oxidation phenotypes."
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A reported extra-mitochondrial pool of HSP60 (~15-20% cytoplasmic, ~80-85%
mitochondrial) is explicitly noted as not yeast-specific, so it does not support a
cytoplasmic localization annotation for yeast Hsp60.
"In broader eukaryotic contexts, HSP60 is predominantly mitochondrial and can also be detected in extra-mitochondrial compartments; one 2024 review summarizes a distribution of ~**80–85% mitochondrial** and ~**15–20% cytoplasmic** for HSP60 (not yeast-specific)."