Elastase-like Activity Is Dominant to Chymotrypsin-like Activity in 20S Proteasome's β5 Catalytic Subunit.
The ubiquitin/proteasome system is the major protein degradation pathway in eukaryotes with several key catalytic cores. Targeting the β5 subunit with small-molecule inhibitors is an established therapeutic strategy for hematologic cancers. Herein, we report a mouse-trap-like conformational change that influences molecular recognition depending on the substitution pattern of a bound ligand. Variation of the size of P1 residues from the highly β5-selective proteasome inhibitor BSc2118 allows for discrimination between inhibitory strength and substrate conversion. We found that increasing molecular size strengthens inhibition, whereas decreasing P1 size accelerates substrate conversion. Evaluation of substrate hydrolysis after silencing of β5 activity reveals significant residual activity for large residues exclusively. Thus, classification of the β5 subunit as chymotrypsin-like and the use of the standard tyrosine-containing substrate should be reconsidered.
Clemens Schöpf Institute for Organic Chemistry & Biochemistry, Technische Universität Darmstadt , Alarich Weiss Str. 4-8, 64287 Darmstadt, Germany.
Dennis
D
Bensinger
Clemens Schöpf Institute for Organic Chemistry & Biochemistry, Technische Universität Darmstadt , Alarich Weiss Str. 4-8, 64287 Darmstadt, Germany.
Theresa
T
Neumann
Clemens Schöpf Institute for Organic Chemistry & Biochemistry, Technische Universität Darmstadt , Alarich Weiss Str. 4-8, 64287 Darmstadt, Germany.
Christoph
C
Scholz
Clemens Schöpf Institute for Organic Chemistry & Biochemistry, Technische Universität Darmstadt , Alarich Weiss Str. 4-8, 64287 Darmstadt, Germany.
Constantin
C
Voss
Computational Biology & Simulation, Technische Universität Darmstadt , Schnittspahnstr. 10, 64287 Darmstadt, Germany.
Sabine
S
Knorr
Institute of Biochemistry CCM, Charité Universitätsmedizin Berlin , Charitéplatz 1/Virchowweg 6, 10117 Berlin, Germany.
Ulrike
U
Kuckelkorn
Computational Biology & Simulation, Technische Universität Darmstadt , Schnittspahnstr. 10, 64287 Darmstadt, Germany.
Kay
K
Hamacher
Institute of Biochemistry CCM, Charité Universitätsmedizin Berlin , Charitéplatz 1/Virchowweg 6, 10117 Berlin, Germany.
Peter-Michael
PM
Kloetzel
Clemens Schöpf Institute for Organic Chemistry & Biochemistry, Technische Universität Darmstadt , Alarich Weiss Str. 4-8, 64287 Darmstadt, Germany.
Boris
B
Schmidt
D020134:Catalytic Domain; D002918:Chymotrypsin / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D006868:Hydrolysis; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D002918:Chymotrypsin; C577981:PSMB1 protein, human; D046988:Proteasome Endopeptidase Complex