National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
GM129539
United States
Citation
Journal: Sci Rep / Year: 2021 Title: Structural basis for the structural dynamics of human mitochondrial chaperonin mHsp60. Authors: Joseph Che-Yen Wang / Lingling Chen / Abstract: Human mitochondrial chaperonin mHsp60 is essential for mitochondrial function by assisting folding of mitochondrial proteins. Unlike the double-ring bacterial GroEL, mHsp60 exists as a heptameric ...Human mitochondrial chaperonin mHsp60 is essential for mitochondrial function by assisting folding of mitochondrial proteins. Unlike the double-ring bacterial GroEL, mHsp60 exists as a heptameric ring that is unstable and dissociates to subunits. The structural dynamics has been implicated for a unique mechanism of mHsp60. We purified active heptameric mHsp60, and determined a cryo-EM structure of mHsp60 heptamer at 3.4 Å. Of the three domains, the equatorial domains contribute most to the inter-subunit interactions, which include a four-stranded β sheet. Our structural comparison with GroEL shows that mHsp60 contains several unique sequences that directly decrease the sidechain interactions around the β sheet and indirectly shorten β strands by disengaging the backbones of the flanking residues from hydrogen bonding in the β strand conformation. The decreased inter-subunit interactions result in a small inter-subunit interface in mHsp60 compared to GroEL, providing a structural basis for the dynamics of mHsp60 subunit association. Importantly, the unique sequences are conserved among higher eukaryotic mitochondrial chaperonins, suggesting the importance of structural dynamics for eukaryotic chaperonins. Our structural comparison with the single-ring mHsp60-mHsp10 shows that upon mHsp10 binding the shortened inter-subunit β sheet is restored and the overall inter-subunit interface of mHsp60 increases drastically. Our structural basis for the mHsp10 induced stabilization of mHsp60 subunit interaction is consistent with the literature that mHsp10 stabilizes mHsp60 quaternary structure. Together, our studies provide structural bases for structural dynamics of the mHsp60 heptamer and for the stabilizing effect of mHsp10 on mHsp60 subunit association.
Evidence: light scattering, We used size-exclusion chromatography (SEC) and dynamic light scattering (DLS) to compare mHsp60 with the double-ring GroEL and single-ring GroEL, microscopy, We used ...Evidence: light scattering, We used size-exclusion chromatography (SEC) and dynamic light scattering (DLS) to compare mHsp60 with the double-ring GroEL and single-ring GroEL, microscopy, We used negative stain TEM and cryo-EM to confirm the assembly
Mass: 55861.137 Da / Num. of mol.: 7 Source method: isolated from a genetically manipulated source Source: (gene. exp.) Homo sapiens (human) / Gene: HSPD1, HSP60 / Production host: Escherichia coli BL21(DE3) (bacteria) / References: UniProt: P10809, chaperonin ATPase
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Experimental details
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Experiment
Experiment
Method: ELECTRON MICROSCOPY
EM experiment
Aggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction
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Sample preparation
Component
Name: Human mitochondrial chaperonin mHsp60 in a heptameric ring conformation Type: COMPLEX Details: Human mitochondrial chaperonin mHsp60 in a heptameric ring conformation Entity ID: all / Source: RECOMBINANT
Molecular weight
Value: 0.060 MDa / Experimental value: NO
Source (natural)
Organism: Homo sapiens (human)
Source (recombinant)
Organism: Escherichia coli (E. coli) / Strain: BL21DE3
Buffer solution
pH: 7.4
Buffer component
ID
Conc.
Name
Formula
Buffer-ID
1
100mM
sodiumchloride
NaCl
1
2
10mM
KHepes
1
3
1mM
EDTA
1
4
1mM
DTT
1
5
5 %
glycerol
1
Specimen
Conc.: 9 mg/ml / Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES / Details: The sample is monodisperse
Specimen support
Grid type: Quantifoil
Vitrification
Instrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE / Humidity: 100 %
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Electron microscopy imaging
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
Microscopy
Model: FEI TITAN KRIOS
Electron gun
Electron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lens
Mode: BRIGHT FIELD / Cs: 2.7 mm / C2 aperture diameter: 50 µm / Alignment procedure: COMA FREE
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