Publication Date:
2010-10-15
Description:
Eukaryotes and archaea use a protease called the proteasome that has an integral role in maintaining cellular function through the selective degradation of proteins. Proteolysis occurs in a barrel-shaped 20S core particle, which in Thermoplasma acidophilum is built from four stacked homoheptameric rings of subunits, alpha and beta, arranged alpha(7)beta(7)beta(7)alpha(7) (ref. 5). These rings form three interconnected cavities, including a pair of antechambers (formed by alpha(7)beta(7)) through which substrates are passed before degradation and a catalytic chamber (beta(7)beta(7)) where the peptide-bond hydrolysis reaction occurs. Although it is clear that substrates must be unfolded to enter through narrow, gated passageways (13 A in diameter) located on the alpha-rings, the structural and dynamical properties of substrates inside the proteasome antechamber remain unclear. Confinement in the antechamber might be expected to promote folding and thus impede proteolysis. Here we investigate the folding, stability and dynamics of three small protein substrates in the antechamber by methyl transverse-relaxation-optimized NMR spectroscopy. We show that these substrates interact actively with the antechamber walls and have drastically altered kinetic and equilibrium properties that maintain them in unstructured states so as to be accessible for hydrolysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ruschak, Amy M -- Religa, Tomasz L -- Breuer, Sarah -- Witt, Susanne -- Kay, Lewis E -- Canadian Institutes of Health Research/Canada -- England -- Nature. 2010 Oct 14;467(7317):868-71. doi: 10.1038/nature09444.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Departments of Molecular Genetics, Biochemistry and Chemistry, The University of Toronto, Toronto, Ontario M5S 1A8, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20944750" target="_blank"〉PubMed〈/a〉
Keywords:
Amino Acid Sequence
;
Hydrolysis
;
Kinetics
;
Magnetic Resonance Spectroscopy
;
Models, Molecular
;
Molecular Sequence Data
;
Proteasome Endopeptidase Complex/*chemistry/*metabolism
;
Protein Folding
;
*Protein Processing, Post-Translational
;
Protein Stability
;
Protein Subunits/chemistry/metabolism
;
*Protein Unfolding
;
Thermodynamics
;
Thermoplasma/enzymology
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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