Rearrangement of the 16S precursor subunits is essential for the formation of the active 20S proteasome.
Proteasome-dependent proteolysis is essential for a number of key cellular processes and requires a sophisticated biogenesis pathway to function. Here, we have arrested the assembly process in its dynamic progression at the short-lived 16S state. Structural analysis of the 16S proteasome precursor intermediates by electron microscopy, and single particle analysis reveals major conformational changes in the structure of the beta-ring in comparison with one-half of the 20S proteasome. The individual beta-subunits in the 16S precursor complex rotate with respect to their positions in the x-ray crystallographic structure of the fully assembled 20S. This rearrangement results in a movement of the catalytic residue threonine-1 from the protected location in 16S precursor complexes to a more exposed position in the 20S structure. Thereby, our findings provide a molecular explanation for the structural rearrangements necessary for the dimerization of two 16S precursor complexes and the subsequent final maturation to active 20S proteasomes.
Mullapudi
Srinivas
S
Department of Biochemistry and Molecular Biology, The University of Texas-Houston Medical School, Houston, Texas 77030, USA.
Pullan
Lee
L
Bishop
Ozlem T
OT
Khalil
Hassan
H
Stoops
James K
JK
Beckmann
Roland
R
Kloetzel
Peter M
PM
Krüger
Elke
E
Penczek
Pawel A
PA
D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D003461:Crystallography / Q000379:methods; D019281:Dimerization; D004789:Enzyme Activation; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008956:Models, Chemical; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry; D046988:Proteasome Endopeptidase Complex / Q000138:chemical synthesis* / Q000648:ultrastructure*; D011487:Protein Conformation; D021122:Protein Subunits; D012336:RNA, Ribosomal, 16S / Q000737:chemistry* / Q000648:ultrastructure*; D013329:Structure-Activity Relationship
D046912:Multiprotein Complexes; D021122:Protein Subunits; D012336:RNA, Ribosomal, 16S; D046988:Proteasome Endopeptidase Complex