Alpha-ring Independent Assembly of the 20S Proteasome.
Archaeal proteasomes share many features with their eukaryotic counterparts and serve as important models for assembly. Proteasomes are also found in certain bacterial lineages yet their assembly mechanism is thought to be fundamentally different. Here we investigate α-ring formation using recombinant proteasomes from the archaeon Methanococcus maripaludis. Through an engineered disulfide cross-linking strategy, we demonstrate that double α-rings are structurally analogous to half-proteasomes and can form independently of single α-rings. More importantly, via targeted mutagenesis, we show that single α-rings are not required for the efficient assembly of 20S proteasomes. Our data support updating the currently held "α-ring first" view of assembly, initially proposed in studies of archaeal proteasomes, and present a way to reconcile the seemingly separate bacterial assembly mechanism with the rest of the proteasome realm. We suggest that a common assembly network underpins the absolutely conserved architecture of proteasomes across all domains of life.
Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan St. Indianapolis, IN 46202.
Dilrajkaur
D
Panfair
Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan St. Indianapolis, IN 46202.
Aishwarya
A
Ramamurthy
Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan St. Indianapolis, IN 46202.
Andrew R
AR
Kusmierczyk
D017124:Conserved Sequence; D017017:Methanococcus / Q000201:enzymology*; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry*; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D040681:Structural Homology, Protein
D050505:Mutant Proteins; D021122:Protein Subunits; D046988:Proteasome Endopeptidase Complex