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Proteasome from thermoplasma acidophilum - a threonine protease

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Seemüller, E., Lupas, A., Stock, D., Löwe, J., Huber, R., & Baumeister, W. (1995). Proteasome from thermoplasma acidophilum - a threonine protease. Science, 268(5210), 579-582.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0010-733B-1
Abstract
The catalytic mechanism of the 20S proteasome from the archaebacterium Thermoplasma acidophilum has been analyzed by site-directed mutagenesis of the beta subunit and by inhibitor studies. Deletion of the amino-terminal threonine or its mutation to alanine led to inactivation of the enzyme. Mutation of the residue to serine led to a fully active enzyme, which was over ten times more sensitive to the serine protease inhibitor 3,4-dichloroisocoumarin. In combination with the crystal structure of a proteasome-inhibitor complex, the data show that the nucleophilic attack is mediated by the amino-terminal threonine of processed beta subunits. The conservation pattern of this residue in eukaryotic sequences suggests that at least three of the seven eukaryotic beta-type subunit branches should be proteolytically inactive. [References: 60]