Abstract
The proteasome is a sophisticated ATP-dependent molecular machine responsible for protein degradation in all known eukaryotic cells. It remains elusive how conformational changes of the AAA-ATPase unfoldase in the regulatory particle (RP) control the gating of the substrate-translocation channel leading to the proteolytic chamber of the core particle (CP). Here we report three alternative states of the ATP-γ-S-bound human proteasome, in which the CP gates are asymmetrically open, visualized by cryo-EM at near-atomic resolutions. At least four nucleotides are bound to the AAA-ATPase ring in these open-gate states. Variation in nucleotide binding gives rise to an axial movement of the pore loops narrowing the substrate-translation channel, which exhibit remarkable structural transitions between the spiral-staircase and saddle-shaped-circle topologies. Gate opening in the CP is thus regulated by nucleotide-driven conformational changes of the AAA-ATPase unfoldase. These findings demonstrate an elegant mechanism of allosteric coordination among sub-machines within the human proteasome holoenzyme.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATPases Associated with Diverse Cellular Activities / chemistry*
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ATPases Associated with Diverse Cellular Activities / genetics
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ATPases Associated with Diverse Cellular Activities / metabolism
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Adenosine Triphosphatases / chemistry
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism
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Adenosine Triphosphate / analogs & derivatives*
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Adenosine Triphosphate / chemistry
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Adenosine Triphosphate / metabolism
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Allosteric Regulation
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Amino Acid Sequence
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Arabidopsis Proteins / chemistry
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism
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Binding Sites
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Cryoelectron Microscopy
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Holoenzymes / chemistry
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Holoenzymes / genetics
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Holoenzymes / metabolism
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Humans
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Kinetics
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Models, Molecular
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Nucleotides / chemistry*
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Nucleotides / metabolism
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Proteasome Endopeptidase Complex / chemistry*
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Proteasome Endopeptidase Complex / genetics
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Proteasome Endopeptidase Complex / metabolism*
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Protein Binding
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Protein Conformation, alpha-Helical
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Protein Conformation, beta-Strand
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Protein Interaction Domains and Motifs
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Proteolysis
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Saccharomyces cerevisiae Proteins / chemistry
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
Substances
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Arabidopsis Proteins
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Holoenzymes
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Nucleotides
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RPT2 protein, Arabidopsis
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Saccharomyces cerevisiae Proteins
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adenosine 5'-O-(3-thiotriphosphate)
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Adenosine Triphosphate
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PSMC4 protein, human
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Proteasome Endopeptidase Complex
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ATP dependent 26S protease
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Adenosine Triphosphatases
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RPT5 protein, S cerevisiae
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RPT1 protein, S cerevisiae
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ATPases Associated with Diverse Cellular Activities