1995/04/28 by Erika Seemüller, Andrei N. Lupas, Daniela Stock +3 · 10 citations
Biochemistry, Genetics and Molecular Biology · #Ubiquitin and proteasome pathways #Glycosylation and Glycoproteins Research #Endoplasmic Reticulum Stress and Disease
paper · doi:10.1126/science.7725107
openalex publication_date 1995/04/28 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/23
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.